INSTITUTE OF NUCLEAR CHEMISTRY & TECHNOLOGY, WARSAW

INIS-mf —14697

PARTICLE TRACK MEMBRANES and THEIR APPLICATIONS

Proceedings of the 3rd CONFERENCE 26-29 OCTOBER 1993

JACHRANKA POLAND

Edited by W. Starosta, M. Buczkowski

VOL 'I 7 Kg a« INSTITUTE OF NUCLEAR CHEMISTRY & TECHNOLOGY, WARSAW

Proceedings of the 3rd Internationa] Conference on

PARTICLE TRACK MEMBRANES and THEIR APPLICATIONS

26-29 OCTOBER 1993

JACHRANKA POLAND

Sponsored by Central Mining Institute, Katowice State Committee for Scientific Research, Warsaw Stefan Batory Foundation, Warsaw

Edited by W. Starosta M. Buczkowski Locnl Organizing Committee:

As. Prof, dr Tadeusz Żółtowski (Warszawa) — Chairman M. Sc. ing. Adam Graczyński (Katowice) — V-ce Chairman Dr Alfred Fiderkiewicz (Warszawa) — Secretary M. Sc. Wojciech Starosta (Warszawa) Dr Marek Buczkowski (Warszawa) M. Sc. Elżbieta Meinhardt (Katowice) Dr Krystyna Cieśla (Warszawa)

This issue is published with the support of the NUKLEONIKA Editorial Office

INSTITUTE OF NUCLEAR CHEMISTRY AND TECHNOLOGY

ul. Dorodna 16,03-195 Warszawa, Poland phone: (0-4822) 11-06-56 or 11-13-13 tlx: 813027 ichtjpl fax: 11-15-32 E-mail ICHTJ at PLEARN CONTENTS

FOREWORD TRACK MEMBRANES, PRODUCTION, PROPERTIES, APPLICATION "Yu.Ts. Oganessian TEMPERATURE RESPONSIVE TRACK MEMBRANES H. Omichi, M. Yoshida, M. Asano, M. Tamada, R. Katakai, R. Spohr, J. Vetter, Ch. Trautmann NUCLEAR TRACKS IN FILMS AND MEMBRANES PREPARATION (abstract only) E.Ferain, R. Legras LATENT TRACK STRUCTURE IN AS OBSERVED BY A HIGHLY SENSITIVEELECTROLYTICAL CONDUCTIVITY MEASUREMENT M. Danziger, A. Schulz, V.V. Trofimov, K. Piokert PHYSICO-CHEMICAL CHANGES IN HEAVY IRRADIATED POLYMER FOILS BY DIFFERENTIAL SCANNING CALORIMETRY K. Cieśla, Ch. Trautmann, E.F. Vansant -INDUCED GRAFTING ONTO PETP TRACK MEMBRANES AND SOME NEW PROPERTIES OF MODIFIED MEMBRANES N.I. Zhitariuk PARTICLE TRACK MEMBRANES AS MODELS FOR BIOLOGICAL CHANNELS C.A. Pasternak, P. Yu. Apel, CL. Bashford, D.T. Edmonds, Y.E. Korchev, A A. Lev, T.K. Rostovtseva, N. I. Zhitariuk PROPERTIES OF PETP TRACK MEMBRANES OF DIFFERENT THICKNESSES P. Yu. Apel, A. Yu. Didyk, I.E. Larionova, T. I. Mamonova, O. L. Orelovich, LI. Samoilova, I.V. Yanina, N.I. Zhitariuk MICROSCOPY INVESTIGATIONS OF SHAPE AND CLOGGING OF TRACK MEMBRANE PORES

O.L. Orelovich, V.A. Altynov, P.Yu. Apel, A Fiderkiewicz; T.I. Mamonova, LV. Yanina, N.I. Zhitariuk COMPUTER SIMULATION OF TRACK MEMBRANES PORES OVERLAP VA Oleinikov pH SENSITIVE MEMBRANES: TRANSPORT PROPERTIES IN AQUEOUS SOLUTIONS OF N.N. Kulov, AN. Nechayew, N.I. Zhitariuk THE MEASUREMENTS OF KCL AQUEOUS SOLUTIONS CONDUCTIVITY IN TRACK MEMBRANE PORES V.V. Berezkin, OA. Kiseleva, V.D. Sobolev, N.V. Churaev, AN. Nechaev TRACKS OF HIGH-ENERGY IONS IN : I. PROPERTIES OF POLUIMIDE IRRADIATED BY HIGH ENERGY IONS Al. Vilensky, V.A. Oleinikov, Yu.V. Tolmachyova, N.G. Markov, E.P. Dontzova TRACKS OF HIGH ENERGY IONS IN POLYIMIDE: II. ETCHING OF TRACKS. PRODUCTION OF POLYIMIDE TRACK MEMBRANES A.I. Vilensky, E.E. Nickolsky, V.A Oleinikov, D.L. Zagorsky, B.V. Mchedlishvili, N.G. Markov, E.P. Dontzova TRACKS OF HIGH ENERGY IONS IN POLYIMIDE: III. INVESTIGATIONS OF ETCHING PROCESS, TRACK STRUCTURE AND PORESFORMS IN THE TRACK MEMBRANES OF POLYIMIDE A.I. Vilensky, E.E. Nickolsky, V.A Oleinikov, B.V. Mchedlishvili, N.G. Markov, E.P. Dontzova TEMPERATURE EFFECTS IN IRRADIATED BY HEAVY IONS L.I. Samoilova, F.Yu. Apel, I.E. Larionova SELECTIVE AND CHEMICAL PROPERTIES OF POLYVINYLIDENEFLUOR1DE TRACK MEMBRANES V.V. Shirkova, B.V. Mchedlishvili, S.P. Tretyakova CREATION OF POROUS STRUCTURE ON CORUND SURFACE AE. Smirnov, D.L. Zagorski, G.N. Gusinski, V.I. Alshits, B.V. Mchedlishvili THE USE OF PARTICLE TRACK. MEMBRANES FOR EPITHELIAL CELL CULTURE (abstract only) D. Root, L.Lawton, H. Lane, K. Casey, J. Clements CHARACTERIZATION OF 0.1 MICROMETER AND SMALLER PORE SIZE MEMBRANES FOR BIOLOGICAL APPLICATIONS (abstract only) D. Root, B. Green, J. Clements, C. Macomber, K. Bates APPLICATIONS OF ION TRACK MEMBRANES FOR PREPARATION OF METALLIC NANO-AND MICROSTRUCTURES (abstract only) J. Vetter OPTICAL PROPERTIES OF STRUCTURE PREPARED ON THE BASE OF NUCLEAR TRACK FILTER TECHNIQUES. PREPARATION OF SUBSTRATES FOR TRACE ANALYSIS BY SURFACE-ENHANCED RAMAN SPECTROSCOPY V.A. Oleinikov, K.V. Sokolov, I.R. Nabiev, T.M. Cotton, RA Uphaus APPLICATION OF PARTICLE TRACK MEMBRANES IN GLUCOSE SENSORS I. Zawicki, M. Buczkowski SOME CHARACTERISTICS OF SPIRAL AND PLATE MODULES (abstract only) G. Dajko, J. Toth PARTICLE TRACK MEMBRANES AS MINICONTAINERS FOR LIQUID CRYSTALS J.Błądek, ARostkowski APPLICATION OF PARTICLE TRACK MEMBRANES (PTM) AS THE SEPARATING LAYER IN FILMY OXIDE CAPACITORS G. Gusinsky, V. Gusev, L. Karpnhina TRACK MEMBRANES IN PLASMAFILTERS. PRODUCTION AND APPLICATIONS B. Zelikson, B. Mchedlishvili, B. Basin, M. Gromov RADIATION RESISTANT J. Bojarski, Z. Bułhak, Z. Zimek LIST OF PARTICIPANTS THE THIRD CONFERENCE

PARTICLE TRACK MEMBRANES AND THEIR APPLICATIONS

Introductory speach by Tadeusz Żółtowski, Conference Chairman

Ladies and Gentlemen, from the whole world, practically. This fact makes our exchange of experiences and This is a great pleasure for me to ideas undoubtfully more interesting. welcome all the participants of the Third Now I would like to present some International Conference on Particle Track comments on the midtidisciplinary areas in Membranes and Their Applications, held science and on such an inherent element of again in Poland. Tliis meeting is the material research as production of the continuation and development of the past particle track membranes. Material activity. Let me allow to remind briefly the research has been based on so-called history: the first conference was organized generic sciences and technologies, such as in Poland, in the Silesian village of mathematical physics and chemistry Jaworze, in May 1989. It was time of applied to industrial systems, new designs revolutionary changes in our country and in and organization methodologies, high Hungary. That first conference gathered performance materials engineering, etc. specialists first of all from the former Soviet Both scientific background and Union (mainly from Dubna), former GDR, technological methods basing on the Hungary, and from Poland. The transformation of matter allow to create introductory contribution entitled "Nuclear and to invent new species and materials Filters" was presented by professor having appropriate physico-chemical Oganessian, but it was the lecture prepared features. In such processes just chemistry together with never forgettable professor and physics play, among other sciences, a Flerov. key role. We should remember that the Two years later, in December 1991, the interfaces of different disciplines very often Second Conference was organized in have been the space of major technological Szczyrk, again in Poland. In this meeting discoveries. also took part specialists from the EC It could be worth quoting, the OECD countries, so it was the first systematic Report on "Science and Technology colloquy of the East and West researches Policy" (1992), chapter "The State of dealing with the particle track membranes Science and Technology in Europe", in (nuclear filters). which it is stated what follows: "The Today we can meet here representatives chemical industry has been one of the most important factors in economic development between fundamenta} chemistry, applied and social changes that have taken place in physics, and other sciences and Western Europe over the last 30 years. This technologies, between chemical industry is an intrinsically innovative sector and other industries. characterized by the manufacture of new In other words, in this case passing from products and materials which integrates the precompetitive research to a and replaces natural ones for different competitive activity was very rapid. Hence, processes and technologies from those basing on this expanse, we can feel that known hitherto. there is an urgent need in Europe and all It is observed that most succesful the countries over the world, to consider the economies have the following features in reflection with regard to elaboration of a common: a well developed technical strategic scientific scheme for fundamental culture throughout society, and in research ir: chemistry and physics. Taking particular in industry, and not confined to into account the importance of material developing scientific skills or training and to research based on the multidisciplinary produce an elite." principle it is appropriate to develop this Chemical and physical methods used for reflection into the perspective of stnictural modifications of materials such implementing and important international as particle track membranes, play an concerialion and co-operation in the essential role in developing high technology European and world-wide dimensions. products, in agrochemistry, biotechnology, The initiative to convene the Third pharmacy, medicine, information Conference on Panicle Track Membranes technology and advanced materials. Tfie and Their Applications and make these problems linked to the environment and conferences known and popular in the pollution could be solved with the help of world is a response for the stressed above particle track membranes. It is, indeed, an challenges. excellent example of the strong interaction TRACK MEMBRANES, PRODUCTION, PROPERTIES, APPLICATIONS

Yu.Ts.Oganessian

Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia

Abstract. The problems of producing track membranes on heavy ion beams of the Flerov Laboratory (FL) are considered. The parameters of the running accelerators and equipment for the of polymer foils are presented. The process of production of track membranes based on different polymeric materials and various applications of the membranes are described. Special attention is given to the principally new applications and devices developed at the Laboratory. This report presents the results obtained by a big group of scientists and engineers working in the field of elaboration, investigation and application of track membranes.

high homogeneity of pore size in the 1. INTRODUCTION produced membrane; The formation of small pores of a given 3. the possibility of varing the geometry at the chemical etching of heavy accelerated ions energy ensures the charged particle tracks in dielectries was production of membranes of different first described by Price and Walker who thickness including those exceeding the investigated the of defects in paths of fission fragments; .[l] Immediately after the discovery 4. the energy, particle charge, angle of made by Price and Walker the track entry into the polymer can be set in such a detection of heavy elements fission way as to obtain micropores of any fragments was used in nuclear physical required parameters. experiments at the Flerov Laboratory for the registration of rare events of very heavy element decay [2]. The method of track detectors developed at the Laboratory within the subsequent period POLYMERIC has served as a basis for the technology of FILM track membrane production. Manufacturing of microfiltration membranes by irradiating polymer films with accelerated heavy ion beams has become an alternative to the method based on the bombardment with uranium fission fragments in nuclear reactors. The advantages of the new irradiation method are: 1. nuclei of accelerated ions are stable TRACK and thus the radioactive contamination of MEMBRANE the irradiated material is totally absent; 2. bombarding particles have the same Fig. 1. Polymer track membrane production (general atomic number and energy, which ensures scheme) I f\*< *"•>• "5Ł""?'!£SŁ-"'* !»* •3Ł «J Table 1. The energies (E) and the average intensities (I) of the ion beams accelerated at tho U-400 Ions 40Ar44 59Co+5 53Cu+6 84Kr+7 E (MeV/a. 5.0 3.9 4.8 3.6 m.u.) 6xlOU 2xl012 1.5xl012 10]2

.., — _ —

physical experiments and polymer membrane production. But. this machine is a very expensive and unique instrument.That is why a small accelerator IC-100 has been built for applied investigations. The beams of B, O, Ne and Ar with an energy of 1 MeV/a.m.u. are available at the IC-100. This machine is used for studying the track formation process and determining the registration threshold in different polymeric materials. The major results are obtained on the U-400. There were investigated the possibilities of obtaining beams of ions which were heavy enough to produce track membranes of different Fig. 2. The U-400 cyclotron polymer films with thickness exceeding 10 fim. The ion beams of 4UAr, Co, Cu and Kr were obtained under The track membrane (TM) production acceleration on the second harmonic of technology includes the irradiation of the accelerating high-frequency electric polymer films on heavy ion accelerators field - the usual mode of operation of the and their physical and chemical treatment U - 400. The parameters of ion beams are (Fig.l). The present report discusses the presented in Table 1. main points of each stage of the TM The krypton ions provide the highest production and the TM properties as well ionization density in comparison with the as considers the main spheres of their other particles given in the Table L The application. use of Kr for irradiation gives a possibility to perforate polyethylene 2. IRRADIATION OF POLYMERIC MATERIALS ON U-400 HEAVY ION ACCELERATOR Fig. 3. The scheme of the irradiation of polymeric films by The FL possesses 4 operating heavy ions on the U - 400 accelerator cyclotrons accelerating beams of light and heavy ions.The mass range of accelerated Verfcol Hnrisonłal deviation ions is from protons to uranium at the plaits (Hale) intensity of the accelerated beams from 2.A.E 10 up to 10 s depending on the mass of the ion accelerated.[3-5] The energy range of accelerated ions is from 0.5 to 100 MeV/a.m.u.. The accelerated beams are used for investigations in the field of fundamental research and for applications. At present, the U-400 cyclotron (Fig.2) is the main heavy ion accelerator for Track membranes,., 9

maximum amplitude of sawtooth voltage - + 50 kV: - magnetic and electrostatic system of vertical beam deviation within the output window with size of 10 cm by vertical (magnetic system: frequency - 200 - 400 Hz, maximum amplitude of magnetic field - 300 Gauss; electrostatic system: frequency - 200 - 400 Hz , maximum amplitude of magnetic field- 300 Gauss, electrostatic system: frequency -1 kHz - 2

Fig. 4. The surface of a track membrano with the hole size of kHz amplitude of sawtooth voltage is 4 100^m 25 kV); - system of ion energy measurement based on semiconductor detectors with the energy resolution + 5%; terephtalate (PETP), polyvinylidene - gauges of ion beam distribution fluoride (PVDF) and polypropylene (PP) within the irradiation zone and also the films with thicknesses of 40, 35 and 50 fiim, ion beam shapes before the input of respectively. Recently a special ion channel for the irradiation of polymeric films was Fig. 5. A scheme of a selectively etched track in a ; a) radial density distribution of the energy transferred to the constructed and the irradiation of mater (by the absorbed dose) around the heavy ion polymeric films and the project of such a trajectory, the dotted line shows the threshold value of the channel was fully realized. absorbed dose, which determines the radius of the selectively etching channel; In Fig.3 a scheme of this channel is b) the etching front of the damaged zone in the heavy ion presented. track. The etching rate along the track VT and the etching There are two special chambers on the rate of the undamaged material VM are shown. The points channel: a machine for continuous indicate the defects of the structure, which appeared after operation with speeds of 0.05 m/s, 0.1 m/s, the passage of a heavy ion through a dielectric 0.2 m/s, 0.4 m/s, 0.8 m/s and 1.6 m/s usually used for homogeneous irradiation of polymeric films with thicknesses from 3 fiim up to 100 fiim, the width of films is not more, than 35 cm. The maximum length of the film (10 ^m) is 2500 m. The irradiation is usually performed in vacuum, but now it is possible to irradiate some materials in the air by using a special stainless steel foil (10 fiim thick) dividing the vacuum volume of the threshold channel and the chamber for irradiation. There is also a start-stop machine for the 0 10 Radius (nm) framed film exposure through a regular shaded mask. In Fig.4 one can see the structure of this type of membranes with regular holes. In this case it is possible to obtain the hole size from 5 fiim up to 100 firn and the thickness of such membranes can be not more than 10 fiim . There are the following systems at the ^dielectric channel: - electrostatic system of horizontal ion beam deviation by 15 cm from the beam axis with the parameters of linear sawtooth voltage: frequency 2 -8 kHz, deviation system in horizontal and vertical together with the increase of specific planes. energy losses and, consequently, with the All the enumerated above equipment growth of the ion atomic number Z (see allows to produce the irradiation with a Fig.6). This enables controlling the pore homogeneity along the length and width shape of nuclear track membranes of films which can be not worse than + already at the stage of irradiating the 5%. In the projected cyclotron complex original dielectric film with multicharged U-TUU + U-400M the accelerator U-400 ions. Thus, for example, in a PETP film of will be used as an injector. In the injection 10 fiim thickness, by using ions of xenon, mode the acceleration at the U-400 will be one can obtain practically cylindrical carried out on the sixth harmonic of the pores with a diameter of several high frequency of the electric field. The thousandth fractions of a micron. [6] The ratio 16 A/Z 36 must be realized in this minimum diameter of the channel (3 - 5 case and the energies of ions must be nm) is fully determined by the size of the from 2.5 MeV/a.m.u. upto 0.5 MeV/a.m.u. zone in the chosen While operating in sucka mode one can material. A further increase of hole accelerate such ions as /J8U,zu/Pb, uyXe. diameter takes place at the chemical The energies of these ions are 0.5 treatment of the irradiated material and is MeV/a.m.u., 1.0 Me/a.m.u., and 1.5 determined by its duration. The diameter MeV/a.m.u., respectively. At the of the pores can be also regulated by the extraction of these ion beams from the choice of the material, type of U-400 cyclotron after the charge exchange bombarding ion, and mode of chemical due to the high value of nuclei charges treatment. exceeding Z S 54, a significant charge dispersion from the equilibrium one with comparable intensites occurs. At the extraction from the accelerator ions with such a charge distribution are separated in the median plane, as a result at the output Fig. 6. The dependence of the track etching selectivity, window an even distribution in the VT/VM, on the parameter characterizing the damage density, (Zcff//j) , wh9re Zeff is the effective ion charge in a polymer, horizontal direction over the width P is relative speed of the ion. Type of the polymer - exceeding 40 crn is practically to be polyethyleneterephthalate. The material was subject to formed. This fact allows the irradiation of ultra-violot illumination polymeric films to be carried out just near the accelerator without the system of horizontal ion beam deviation. By the mentioned above procedure the Xe and Pb beams with the energy enough for producing track membranes of up 20 fiim thicknesses can be obtained.

3. TRACK MEMBRANE PRODUCTION. PROPERTIES OF TRACK MEMBRANES Along the ion trajectory in the dielectric a radiation damage zone appears which is called latent track. In this zone the material has a decreased density and is characterized by an increased etchability (Fig.5). The ion specific energy losses determine the degree of structure changes and the etching rate VT of the material in the track. The etching selectivity, i.e. the ratio of the track etching rate and the bulk etching rate of the material itself, VM, quickly increases Track membranes, 11

To increase the etching rate ratio, polyimide, polyarylate, cellulose nitrate, some polymer materials (such as, for polyaliylglycol carbonate, mica, has been example, polyethyleneterephthalate and developed. For a number of years already ) are subjected to the Flerov Laboratory produces track ultra-violet sensitization in the presence membranes using the of oxygen or are treated with a solvent polethyleneterephthalate film. It is specially selected for this material.[3,5] In characterized by high mechanical the first case there takes place the strength, resistance to many solvents, photooxidation of radiolysis products in acids, oxidizers, diluted alkalis at room the tracks. In its stead this increases temperature, high radiation resistance substantially the track etching rate, (resists the absorbed dose reaching l(r ensures the cylindrical shape of pores, kGy). The size of pores in decreases the dispersion of channel pofyethyleneterephthalate track diameters, increases the track membrane membranes can range from 0.015 to 10 permeability. At a certain wavelength of jum . The porosity fi.e., the part of the ultra-violet irradiation the photooxidation membrane surface occupied by the pore process takes place only in the tracks, and holes), is usually from 5 to 20% and varies does not affect the polymer around. In depending on the practical task for which the second case the sensitizing effect of the membrane is intended. The standard the solvent is caused by the removal of track membrane thickness is 10 but, fragments of fractured macromolecules nevertheless, there can be manufactured from the tracks and to morphological membranes both of larger and smaller changes of the polymer in the region thicknesses (20 - 50 /urn ). For many around the track. After the sensitization applications of polyethyleneterephthalate the material is subjected to a track membranes the fact that they can corresponding chemical treatment resist both thermal (boiling, autoclaving), (etching), then the obtained membrane is and chemical treatment (with alcohol, washed and dried. ethylene oxide, formalin, mixture of The modes of physical and chemical peroxide and formic acid) is the most treatment (sensitization, etching) are important. determined by the properties of polymers chosen for the production of the track membrane. In its turn this or that polymer Fig. 8. Pore size distribution in a track membrane with an is selected depending on the task, i.e. with average size of pores — 1 .Opm the account of the properties - chemical, thermophysical or some others, which are to characterize the produced membrane. The method of producing track membranes from the following materials: polyethyleneterephthalate, polycarbonate, polypropylene, PVDF,

Fig. 7, Electron microphotographic picture of the TM surface

0.8 1.0 1.2 Pore diameter (/zm) 12 Yu. Ts. Ogaiwjsslan

Fig. 9. The electron mlerophotographlo picture of the TM F'O. 10- Polyatereno Latex particles rotainod by tho surface aftor filtering on ampoullod morficnl propnrntlon memebrune at the filtration of a Latox suspension

Measurements with an electron Due to the small thickness (usually microscope show that the track about 10 fim) track membranes provide membrane pores are rather uniform in the same flow rate of a liquid or a gas as their shapes and size (see the photo in the best membranes produced by other Fig.7). The spread of pore diameters is methods (see Fig.12). The compactness of usually only 2-5%. The curve of pore the structure brings around another distribution according to their size rather useful property of track obtained through the analysis of the membranes: as compared with other electronic microscope picture of the track membranes they have do not sorb the membrane surface is presented in Fig.8. substances dissolved in the filtered liquids The indicated structural peculiarities [7]. This allows to prevent the possible ensure the high selectivity of track losses of filtered reagents, for example, membranes at the separation of disperse the losses of protein at the filtration of systems, i.e., the ability to retain particles biopreparations. On the other hand, the of size exceeding the pore size and to let membrane matrix does not contain, through smaller particles, This property practically, any components capable of manifests itself most strongly at filtering migrating into the filtrate and, liquid disperse systems. The retained consequently, of contaminating it with particles are collected on the smooth outside admixtures. surface of the membrane which makes it The technological complex for physical most convenient to investigate them and chemical treatment of the irradiated further using microprobe analysis polyethyleneterephthalate film comprises methods, optical and electron microscopy now six set-ups for ultra-violet exposure (Fig.9, 10 and 11). One can assert that at and four etching machines (Fig.13). It the liquid media filtration the membranes ensures the production of 100 000 square of this type are the only true screening meters of track membranes a year. The filter, i.e. the one which ensures the technology of polyethyleneterephthalate separation of particles only on the membrane production has been tested in surface. This makes it possible to every aspect, optimized and is successfully regenerate easily the membranes in the used for over 10 years. process of their utilization by creating a The membrane quality is controlled turbulent flow of filtered liquid along the during the production by means of the membrane surface or by means of following methods: supplying for a short time of a reverse - measurement of the "bubble point"; flow.[7] - measurement of the gas permeability; Track 13

Fig. 11. Bacteria cells on the surface ofTM

-determination of the membrane burst strength; - determination of the pore diameter and pore density by means of the scanning electron microscope; - the control of pore size distribution with a Coulter II porometer. Track membranes based on other polymers (PP, PVDF) are produced on the laboratory scale. The developed in the Lab original methods of track membrane production from chemically stable polymers [8,9] include special methods of sensitization, etching and additional treatment of membranes necessary to clean the matrix from inorganic admixtures (traces of etchants). At present we are capable of working out PP and PVDF membranes with the pore diameter of 0.1 fim and more. The experiments have shown that the PP and PVDF membranes possess substantial advantages at the filtration of aggressive

media (see Fig. 14). The prospects of their 0.02 0.05 0.1 0.2 0.5 1.0 2.0 application are linked with processes of Pore size, Jim purification of ultra-pure reagents (acids, bases, solvents) and aggressive gaseous Fig. 12. Permeability of track membranes for pure water media used in microelectronics and other and air measured at the differential pressure of 1 bar as a branches of modern industry. function of the pore diameter On the other hand the chemical properties of polyethyleneterephthalate membranes can be also changed by means of grafting monomers with required [10-12] By grafting these or those characteristics on the surface. Thus the substances one can change the surface radiation-induced grafting of styrene can properties of track membranes increase the resistance of PETP (wettability, sorbtion properties). membranes to media with a high pH. HCI PU PP x K ca PVDF z UJ 1- CU d=0.2 /IM

Ul 0 10 20 50 40 50 60 70 en M TIME (DAYS)

Fig. 13. The technological equipment for the production of the PETP track memobranes T. PVDF. <3 Ol I— PŁI d=0.2 /IM 4. APPLICATION OF TRACK MEMBRANES co AND TRACK-MEMBRANE BASED PRODUCTS 0 10 20 30 40 50 60 70 Track membranes find wide TIME (DAYS) application which is predetermined by their main properties: they possess a set Fig. 14. The change of the mechanical strsnght of PETP, PP threshold of microparticle retention which and PVDF track membranes at a long contact with in its turn varies within wide limits aggressive gases — hydrogen chloride and ammonia used (Fig.15). at the production o! semiconductors One of the most traditional applications of track membranes is the [RACK MEMBRANES POFT SIFT Oi'n) purification of deionized water from 10 microparticles. The deionized water O 01 should have a specific resistance of 18 MOhm-cm, the organic substances content below 0.2 mg/1 and not more than 2 microparticles of 1 fim size per 1. The -TC6ACC0 SMOKE - main advantages of track membranes at -CAM0H Dusr- the final purification of technological -CUflWH 81ACK- • crEsnirf - water is the low volume of the filtered 01 COMSUSTKW. media spent for washing of the membrane " PR0DUC1S and the rigidly set threshold of microparticles retention. Usually they are Fig. 15. Relative sizes of small particles compared with track using for the final purification in the form membrane pore diameters of cartridged filters containing from 1 to 2.5 square meters of a track membrane. A ten inch cartridge (see Fig.16) with a track membrane ensuring the retention threshold of 0.2 jum provides the filtration rate of 5001/hr and possesses the resource of up to 5 cubic meters for operation with a filtrate. Cartridges are tested by the bubble point method and the method of the flow through the wetted membrane. Fig.17 presents the characteristics of cartridges based on two PETP track membranes with one of them possessing larger pores being used as a pre-filter. Fig. 16. TM-based cartridges used for the filtration of liquids Track membranes, 15

Track membranes are widely applied for the investigation of the erythrocyte deformability. Membranes with a pore diameter of 5 fj.m is an ideal test-object for the purpose. By measuring the rate of the blood passing through the pores the size of which is a bit smaller than that of the red corpuscules one can make an accurate conclusion on their state. Another important application of track membranes in medicine is the separation of the blood plasma (plasmapheresis).[7] This process is carried out on membranes with a pore diameter of 0.7 jum. Woter Flow Rote (LPMl Another example of filtering liquids Fig. 17. Differential pressure vs water flow rate through tho with track membranes - is the cartridges with two PETP membranes. 1 -0.45 and0.2^m; 2 purification of crystallizing solutions. A - 3,0 and 0.2,um. The membrane surface area is 1 mz. detailed study of the quality of potassium dihydrophosphate monocrystals has demonstrated that the scattering of light in a crystal can be substantially decreased by means of filtering the initial solution through 0.6 - 0.7 fim pores. The

Fij,. 19.1- Round fitter housing

i

Fig. 18. Stainless steel filter holder. Filter size is 142 mm

Track membranes with the 0.2 fim pore diameter and cartridges based on these membranes were used for sterile filtration of test microbe cultures: E.Coli, Staphylococcus aureus and others. At the filtration of 5 1 of the suspension with the microorganism concentration of 3 x 10 cm" there were always obtained sterile preparations. application of track membranes in the technology of rapid growing of crystals enable to increase the resistance of solutions to mass crystallization with a simultaneous simplification of the filtration equipment [13]. High selectivity of track membranes ensures the effective concentration and purification of virus culture suspensions for example of the rabius virus.][7 ] The virus suspension is concentrated by means of membranes with pore diameters from 0.05 to 0.1 fim. After repeating the concentration several times and diluting anew the concentrate with a buffer solution they obtain a preparation in which the content of admixtures is 500-600 times smaller and concentration of virus is by one order of magnitude higher than the initial one. At the final stage concentrated and purified suspension is subjected to clarification by passing it through a track membrane with a pore diameter of 1.5 fim. Track membranes are most convenient for the qualitative and quantitative analysis of the sediment accumulated in the process of filtration. This is the basis for applying track membranes in the environment contamination studies, in the studies of pharmaceutical preparations, microflora and microfauna purity, of the condition of clean work-rooms, etc. 0_ 6 [3,4,7,14,15] For the filtration of liquids °0.0 0.5 1.0 V.5 2^0 2^5 3.0 7.5 there have been developed a number of Particle size, urn devices equipped with track membranes. These are flat filter holders (membrane Fig. 21. The efficiency of aerosol microparticles retention by track membranes with different pore diameters as a diameters are 142 and 293 mm) designed function of particle size. The measurements have been for small volumes of the filtred media performed with a LAS-X counter at the flow rate 0.1 cm/s (Fig. 18). For filtering large volumes they are using set-ups with a different number aerosol particles, i.e. they are of cartridges (Fig.19 and 20). characterized by a very low level of their Filterholders for the tangential flow of own dusting. Possessing track membranes liquids are being developed. of such unique properties, used in Recently substantial progress has been filtering devices, one can clean the air of gained in the application of track class 100 to class 1. The service life of the membranes for the purification of membrane is here reaching 2 years.[16] gaseous media as well. In contrast to the The uniqueness of the TM structure filtration of liquids at the collecting of attracts interest to them as to model microparticles from the gas phase, track microporous bodies. In this aspect they membranes retain to a large extent the find diverse applications in the particles with diameters which are much experimental investigations in the field of smaller than the pore diameter (Fig.21). condensed media physics, optics, colloidal In this case the membranes themselves chemistry, microbiology and other produce practically zero amount of branches of science [17-21]. Track membranes, 17

8. Tretyakova S.P.,Shirkova V.V., 5. CONCLUSION Khitrova N.N. et al. Nucl. Tracks, This report gives only some 1986, v.12,75-76. fragmentary information about the 9. Apei P.Yu., Shirkova V.V., Soboleva properties and applications of TMs T.I. et al. Vysokochistye veshchestva, obtained by means of heavy ion 1990, No.2,105-107 (in Russian). accelerators. We have not set for 10. N.I. Zhitariuk, P.A. Zagorets and V.I. ourselves the task to enumerate Kuznetsov. J.Appl. Polym. Sci., 1990, absolutely all the possibilities and fields of v.40,1971-1980. TM application (this can be found in ll.N.I.Zhitariuk and N.I.Shtanko. original papers). We would like to note Polymer,1991, v.32, 2406-2410. that TMs are a substantial addition to the 12. N.I.Zhitariuk, V.I. Kuznetsov and N.I. existing membranes and methods. TMs Shtanko. Environ. Protec. Eng. 1989, may be also utilized in combination with v.15. ili-119. conventional membranes and methods 13. V.I. Bredikhin, A.B. Vasiliev, G.L. which ameliorates significantly the Galushkina et al. Vysokochistye characteristics of processes where the veshchestva, 1990, No.2, 116-120 (in issues of high selectivity and purity of Russian). media are of utmost importance. 14.S.B. Tambiev and L.L.Demina. Oceanologia, 19S2, v.22, 137-142 (in REFERENCES Russian). 1. P.B.Price and R.M.Walker. Phys. 15. G.N.Flerov, T.I. Mamonova, Rev.Lett., 1962, v.8, 217-219. N.F.Karzhavina et al. Preprint JINR 2. V.P.Perelygin, S.P. Tretyakova and 18-87-598, Dubna, 1987,1-7. I.Zvara. Preprint JINR 1323, 1963, 16. V.V. Ovchinnikov, I.A. Belushkina, Dubna, 1-8. E.D. Vorobiev et al. Preprint JINR 3. G.N.Flerov. Vestnik Akademii Nauk Dl 8-90-443, Dubna, 1990, p.1-9. SSSR,1984, No.4, 35-48 (in Russian). 17. F.M.Aliev, I.K. Meshkovskij and V.I. 4. G.N.Flerov and Yu.Ts.Oganessian. In: Kuznetsov. Doklady Akadimii Nauk Proc.Intern. Workshop on Track SSSR, 1984, v.279,848-851 (in Membranes and Their Application in Russian). National Economy. (Eds. W. Starosta 18. P.Yu.Apel, V.I.Kuznetsov and and T.Żółtowski), 1989, 8-14 (in V.V.Ovchinnikov. Kolloidnyj Zhurnal, Russian). 1987, v.49,537-538 (in Russian). 5. G.N.Flerow, P.Yu.Apel, AYu.Didyk 19. V.V.Beriozkin, A.N.Nechaev, S.V. et al.Atomnaja Energia, 1989, v.67, Fomichev et al. Kolloidnyj Zhurnal, 274-280 (in Russian). 1991. v.53,339-342 (in Russian). 6. P.Yu.Apel. Nucl. Tracks, 1982, v.6, 20. L.N. Moskvin, A.N. Katruzov, V.S. 115-118. Gurskij et al. Doklady Akademii Nauk 7. G.N.Flerov and B.V. Mchedlishvili. SSSR, 1988, v.302, 841-844 (in Zhurnal Vsesojuznogo Russian). Khimicheskogo Obshchestva imeni 21. A.V. Mitrofanov, F.A. Pudonin, T.I. Mendeleeva, 1987, v.32, 641-647 (in Gromova et al. Nucl. Instrum. Meth., Russian). 1991, v. A308, 347-351.

TEMPERATURE RESPONSIVE TRACK MEMBRANES

H. Omichi, M. Yoshida, M. Asano, M. Tamada, R. Katakai*, R. Spohr**, J. Vetter**, Ch. Trautmann**

Japan Atomic Energy Research Institute, Takasaki Radiation Chemistry Research Establishment, Takasaki, Gunma 370-12, Japan * Faculty of Engineering, Gunma University Kiryu, Gunma 376, Japan ** Gesellschaft fur Schwerionenforschung mbM. Postfach 110552.D-6100, Darmstadt,FRG

ability to change their volumes when 1. INTRODUCTION environmental stimuli such as Particle track membranes (PTM) have temperature, pH, electric fields are a narrow size distribution of pores of imposed [2,3]. These changes are cylindrical shapes. This characteristic accompanied by the absorption and makes PTM enable to differentiate desorption of water by the gels. There is articles of similar dimensions precisely. a critical temperature called "lower TM has been applied to separating critical solution temperature LCST" at biological cells, filtering polluted air which an abrupt change in volume of the streams, stabilizing beverages, etc.[l]. The gels occurs [4]. The theoretical treatment pore size of PTM, however, is of the changes has been studied [5]. Even unequivocally decided by the irradiation the applications of these changes have conditions of heavy ion beams and the been tried to realize artificial muscles, following chemical etching. If PTM is biosensors, etc.[6]. provided with a flexibility of pore size The present report intends to show the which changes depending on the changes possibility of synthesizing such in such environmental conditions as pH, membranes by combining PTM with the temperature, electric field, etc., the hydrogel. One of the conveniences of application of PTM would be expanded. applying hydrogels as the polymer to It might be possible to control a micro modify PTM is the ease of changing the flow through the membrane, which is properties by choosing the appropriate carried out inside living organisms under chemical structure of the repeating unit various inher and outer conditions. One of the polymer gels. In the present study, of the possible approaches to realize such the hydrogel that was obtained by the a sophisticated membrane is combining polymerization of an acryloyl or PTM with a polymer of a different methacryloyl monomer containing amino characteristic responding to these acid groups in its repeating unit was used. environmental conditions by means of The reason to choose such a hydrogel chemicaly bonding the polymer to the containing amino acids is based on the pore wall. fact that specific characteristics of living Hydrogels are known to possess the organisms responding to environmental conditions are highly dependent on the presence of various types of amino acids in the forms of proteins, enzymes, etc. 3000 2000 2. AMIN O ACID CONTAINING HYDROGELS 1000 The acryloyl or methacryloyl monomer containing amino acid unit was * 300 synthesized as follows: methyl ester of 200 c amino acid hydrochloride was dissolved in 5 100 chloroform containing triethylamine. % Acrylic or methacrylic acid was added to tf) the solution diluted with tetrnhydrofuran. 30 Then, dicyclohexyl-curbodiimide was 20 added to the solution kept at a low to : m-rjDHD—ur^lHiHp—nr?- 3 temperature with agitation. The : i • • i—i—j—i—>— precipitate of dicyclohexylurea was 20 40 60 80 removed by filtration to give a raw material of amino acid containing acryloyl Temperature CO or methacryloyl monomer. The Fig. 2. Degree of swelling of methacn/lol amino acid polymerization of the purifed monomer containing polmer gels treated for 24h at each temperature was carried out by irradiating the after preswelling at 0°C for 3 weeks: methyl esters of (1)glycine, (2)alanine, (3)valine, (4)isoleucine and monomer solution with gamma rays from (S)alanfne, (6}alanine ethyl oster, (7)a!anine butyl ostor, (B) cobalt-60 at room temperature [7J. The alanine benzvl ester polymer obtained with a small dose (less than lOOkGy) was dissolved in water at low temperature. Above LCST, however, ester as shown in Fig.l for example and it precipitated from the water solution. by the evolution of an endothermic peak This change was followed by the decrease in the DSC curve due to the phase in transmittance of visible light at 500 nm transition [8], It was observed that the in the case of acryloyl-L-proline methyl polymer size reversibly changed according to ' the temperature change. This monomer was copolymerized with a small amount of such a crosslinkable monomer Fig. 1. Changs in transmittance at 500 nm of aqueous as polyethylene glycol diniethacrylate solution of tho polymer gol of acrylol-L-prolino methyl cstor under a similar procedure mentioned 100 r above. The copolymer obtained was no more soluble in water. A large amount of water was absorbed by the copolymer 90 • below LCST. Above LCST, on the other hand, the water was released from the 80 copolymer. This change can be followed by the weight measurement of the ue c copolymer. The water uptake thus o 70 obtained is indicated as the degree of e swelling of the copolymer in Fig.2. The 60 degree of swelling depends on what kind of amino acid group and two adjacent 50 alkyl groups are included in the monomer unit. The balance between a hydrophilic group and a hydrophobic group and that between two different hydrophobic groups are responsible to this change. Ł JL The change in swelling with the change in 10 20 30 40 50 temperature was reversible. Temperature CO Temperature responsive., 21

3. PREPARATION OF THERMO-RESPONSIVE MEMBRANES 10 The commercially available CR-39 is known as a polymer with a high sensitivity 8 to the irradiation of heavy ions. It is IP possible to produce cylindrical pores by the irradiation of heavy ions of high i« energy and the following chemical etching with an alkali solution. For synthesizing a J 4 membrane of porous structure with a £ function responding to temperature 5 change, CR-39 was selected as a raw a. 2 material. Two processes as shown in Fig.3 were tried. In Process 1, diethyleneglycol-bis-allylcarbonate, the 0< monomer unit of CR-39, and the amino 0.0 0.5 1.0 1.5 2.0 2.5 acid containing monomer were Tfme[h] catalytically copolymerized. Then, the Fig. 4. Pore diameter and etching time with 6N NaOH copolymer film was irradiated by such solution at 60°C heavy ion beams as Au of the energy ca. lOMeV/u and subject to the following chemical etching with 6N NaOH solution copolymer and CR-39. In both cases, the at 60° for 6 h. In Process 2 the pore diameter changes linearly with the homopolymer film of etching time. The growth rates of pore diameter obtained from the slopes are diethyleneglycol-bis-allycarbonate which 33.6 and 1.1 ^m/h for the copolymer film was preliminarily irradiated with heavy and CR-39, respectively. The necessary ion beams and etched with the alkali etching time to obtain the same pore solution was used as a raw material for diameter is, therefore reduced by a factor the further chemical modification of ca. 1/30 by copolymerizing amino acid procedure. The amino acid containing containing monomer. The cross-sectional acryloyl monomer was graft polymerized view of the pore observed by the scanning onto the porous membrane either by the electron microscopy indicated that the method of radiation-induced copolymer film possessed cylindrical polymerization or photo-induced polymerization [9-11]. 4. CARACTERISTICS OF THERMO-RESPONSP7E MEMBRANES The copolymer film which was irradiated with heavy ion beams was chemically etched. Fig.4 shows the comparison of etching speed between the

PROCESS 1 PROCESS 1

I Menenwr I CR-3» film

0.93 0.97 1.01 1.05 1.09 • 0.95 0.99 1-03 1-07

Fig. 5. Distribution of pore diameter expressed by D/Dav for CR-39 and copolymer film containing methacrylol L-alanine Fig.3. Preparation of thermo-responsive membranes methyl ester pores when the sensitivity expressed by on the fact that the layer of the Vt/Vh-1 was sufficiently large. The pore thermo-responsive hydrogel is localized size distributions are shown in Fig.5. on the surface of pore. Then, only the Comparing the pore size distributions of pore region is able to respond to the CR-39 and copolymer, that of the stimulus from outside. The response time copolymer was a little broader. One of the in this case, however, depend on the reasons of the expanded distribution may amount of the hydrogel layer. The smaller be attributed to the mixing of the the amount of the hydrogel is, the quicker radiationsensitive component of CR-39 is the response. with the amino acid containing hydrogel The combination of such a layer in the copolymer. thermo-responsive pore structure makes The porous membranes obtained by it possible to apply the membrane to such Process 1 and Process 2 were dipped in field as control of a micro flow through water. Fig.6 shows that the water uptake the pore by changing temperature, pH, of the copolymer membrane changes electric field, etc. Schematic changes in between 0% and 30% when the stepwise flux with these two type of porous change in temperature of the outside membranes are shown in Fig.7. In the water is repeated between 0°C and 60°C. case of the membrane obtained in Process Along with this cyclic change, the pore 1, the flow can be changed within a size changes reversibly. The maximum certain range. The presence of the and minimum pore size were ca. 16 fim maximum and the minimum of the flow in and 14 ^m, respectively. The time this case is due to the residual pore size constant of the thermo-response of pore even at the temperature providing the size change was not equal between the utmost shrinking. With the membrane two steps of increasing and decreasing obtained in Process 2, on the other hand temperature. That is, the former was the gate is controlled from the complete ca.10 min while the latter was 24 h. A shut off state to the maximum open state. complete closure of the pore was In near future this technique will be observed with the graft membrane. The applied to the realization of distinguishing maximum pore diameter was 1.2 fim. The one molecule from the other of similar possibility to realize such an on-off size with different chemical affinity by characteristic with this membrane is based introducing a hydrogel component which Temperature responsive. 23 has a specific affinity to a certain 6. Y.Osada, J.Intell. Mater. Syst. and molecule. Struct., 4, 50 (1993). 7. M.Yoshida, M.Tamada, M.Kumakura, REFERENCES and R.Katakai, Radiat.Phys.Chem.38, 'L Proceedings of the 2nd Meeting 7(1991). "Particle Track Membranes and Their 8. M.Yoshida, H.Omichi, and R.Katakai, Applications", 1991, Poland. Eur.Polym.J, 28,1141(1992). 2. D.J.Hemker, V.Garza, and 9. M.Tamada, M.Yoshida, M.Asano, C.W.Frank, Macromolecules, 23,4411 H.Omichi, R. Katakai, R.Spohr, and (1990). J.Vetter, Polymer, 33,3169(1992). 3. S.Beltran, H.H.Hooper,W.Harvey, 10. M.Tamada. M-Yushida, M. Asano, H.W.Blanch, and J.M.Prausnitz, H.Omichi, R.Katakai, Ch.Trautmann, J.Chem. Phys., 92, 2061 (1990). J.Vetter, and R.Spohr, Nucl.Tracks 4. F.M.Winnik, H.Ringsdorf, and Radiat. Meas., 20,543(1992). J.Venzmer, Macromoiecules,23,2415 11. M.Yoshida, M-Tamada, M.Asano, (1990). H.Oniichi, H.Katakai, R.Spohr. and 5. T.Tanaka, I.Nishino, S.T.Sun.and J.Vetter, Radiat. Effects and Defects S.V.Nishino, Science, 218,467(1982). in Solids, 126,409(1993).

NUCLEAR TRACKS IN POLYMER FILMS AND MEMBRANES PREPARATION

E. Ferain and R. Legras

Unitede Physique et de Chimie des Hauts Polymeres, Univers'rte Cathoiique deLouvain, Croix duSud, 1,1348, Louvain-la-Neuve, Belgium

Abstract. The chemical modifications induced by energetic heavy ion irradiation of polycarbonate (PC) film are determined by GPC, HPLC, ESR, TGA, 1R and UV spectrophotometries. The main results of the irradiation are radical creation, chain scission, cross-linking and appearance of new chemical groups in the main polymer chain. As far as the creation of new groups is concerned, they are determined by means of a model compound of PC : the diphenyl carbonate (DPC). The following compounds are identified after energetic heavy ion irradiation of DPC : salicylic acid, phenol, 4,4'-biphcnol, 2,4' -biphenol, 2,2'-biphenol, 4-phenoxyphenol, 2 - phenoxyphenol, phenyl ether, phenyl benzoate, phenyl salicylate, 2-phenylphenol and 2-phenoxyphenyl benzoate. A similarity between the heavy ion irradiation and a heat treatment has also been established with DPC. On the basis of these results, we try to give an explanation of the preferential attack along the tracks of the irradiated film. Also, an explanation of the well-known beneficial effect of an UV exposition of the irradiated film on the selectivity of this preferential chemical attack is suggested.

LATENT TRACK STRUCTURE IN POLYMERS AS OBSERVED BY A HIGHLY SENSITIVE ELECTROLYTIC\! CONDUCTIVITY MEASURMENT

M.Danziger*, A.Schulz*, V.V.Trofimov**, K. Prokert***

Joint Institute for Nuclear Research: * Flerov Laboratory of Nuclear Reactions **Laboratory of High Energy Physics ***Dresden University of Technology, Instrtut fur Strahlenschutzphysik

Abstract, First results of a new electrolylical conductivity cell are reported concerning the initial stage of the pore opening process during track etching in vitreous solids. On the basis of the soft mode (low energy excitation) model for track etching, sec ref.[4], a distribution function for the number of performed micropores as function of time is calulated, by accounting for the radial etch rate as function of the effective pore radius.

of the voltmeter, an amplifier with 1. INTRODUCTION variable gain steps 1,10,100 and 1000 has The interaction of heavy ions with been used. Furthermore, programmable solids (thin films) produces a narrow devices such as a sine generator, a cylindrical core of primary damage. The scanner, and a voltmeter, are installed in actual nature of the damage and the order to carry out various measuring mechanism of its formation is not fully methods. Fig. 1 represents the modified understood. In some recent publications, experimental set-up. Another significant see refs [1,2,3,4], a new model was difference to the measuring principle used introduced based on the assumption that until now, is the introduction of the direct the incident ion causes a disturbed voltage method. Since foil capacity structure adjacent around its trajectory influence can be eliminated by applying characterized by vitreous properties, the current, this method is useful especially in model of low energy excitations. The new the range of very high foil resistance. experimental set-up described here is During opening of the first pores, sufficiently sensitive to allow to measure associated with a high foil resistance, the initial stage of the radial etch process electrolytical effects can be neglected, and to determine the systematics of the because during this phase, currents are pore formation. too small to cause chemical electrode polarization. When the foil resistance 2. MODIFIED ACTUAL ADVANCED reaches about some MQ, the a.c. voltage EXPERIMENTAL SET-UP method is started, otherwise would The substitution of the fixed reference distort, the measurement. resistance by a resistance decade and a lock-in amplifier is the most important Fig.3 represents the time function of change of the former set-up. The the foil resistance obtained by the resistance decade, consisting of five modified experimental set-up. Since the resistances about 100 Q, 1 kQ, 10 kQ, 100 part of the curve close to the transition k£2, and 1 MQ, enables to adapt to the point from dc to ac measurement can be time-dependent foil resistance over a differentiated, the whole function R(t) wide range. For optimizing the sensitivity can be used to calculate the time 28 M. Danzigcr et al.

incorrect. By means of the model of low energy excitation [4,5,6,7] it is possible to derive the time distribution, of the number of the opening pores Nexp = N(t). To calculate this distribution the

voltmeter following steps are necessary: - Fit the model parameters with the experimental data in the interval [rv.rL] (see Fig.5); - Extend calculateded curve to values smaller than rv;_ - Calculate r(t) from theoretical etch rate vr. These values are defined as rice (t) (lee-low-energy excitations).

re'cimee ruiitmcc The corrected r(t)-curye turns asymptotical to a constant r-value of about 0.2 nm. In the case of a single pore, lanertfor N=l and r - r, this value can be «ltctrodt interpreted as the smallest measurable foil radius of the pore at the beginning of its «ll opening process. ctchtnt H)0 WC 3. CONCLUSION By means of the model of low-energy-excitations, the following Fig. 1. Topical measuring system for investigations of interpretation of the functional smallest etching micropores dependence of the radial etching rate of heavy ion tracks in polymers on the pore dependent pore radius and its time radius can be given: derivative. This is shown in Fig. 4. The - in the range 0 < r < rv(rv = 5 nm): differentiation of effective r(t) - curve [7], The structure of the matter has corresponds to the etchrate, as function of features of a vitreous solid, i.e. local the effective radius, shown in Fig. 5. For polarized regions should exist depending calculating f(t) , the number of the on the radius of the pores. With perforated pores N is assumed to be increasing pore radius, the size of the constant. Since during etch the pores do polarized regions is growing too. The not break through simultaneously, and reason for this is shown in Fig. 5 therefore a time dependent_size N(t) has representing the dependence of the radial to be considered, for values r

Rrcf -cu—cz

o . — lit Ur

If, v. X 1

Fig. 2a. Equivalent circuit in the case of direct voltage Fig. 2b. Equivalent circuit in the case of alternating voltage measurement measurement Latent track structure in.. 29

Fig, 3. Time dependence of the foil resistance. The arrow shows the begin ol the measurement with alternating voltage method

10 10 ' 10 ' 10 ' t [s]

6 jiio

10 -'L-L. 10 •"

Fig. 4. Tha measurement effective radius in dependence on Fig. 5. The etching rate versus the effective radius of etched the time pores

10 4 t (sj t [s] Fig. 6. The number of opened pores as function of time Fig. 7. The measured and corrected effective pore radius

Iocai free charges, corresponding oto the Transition to the undisturbed structure. locally polarized regions of, see ref. By means of the model of low-energy [5,6,7]. The peak in Fig. 5 can be excitations it is possible to determine the explained by a high local density of free ore opening as function of time (see charges in this range, associated with a Pig.6). The measurements indicate that high radial etch rate. the pore opening during etching has a - for the range rvsr< rp: regular behaviour. Further justification of In comparison with the undisturbed this behaviour will be the subject of future material this region has a deficit of work. localized free charges. That is the reason Taking into account the time of the minimum in Fig. 5 in our model. distribution N(t) of the pore opening

- for the range r > rp: process, the effective radius function r(t) can be corrected. The constant r-value at 3. Danziger M., Bernhardt A., Phys. Stat. the beginning of the pore opening process, Sol. (b) 1992,169, p.591 shown in Fig.7, can be interpreted as a 4. Danziger M., Andrassy G., Phys. Stat. smallest measured effective radius of an Sol. (b) 1990, 223, p.161 already opened pore. This limit in value 5. Andrassy G., Danziger M., can be explained by the finite sizes of the Communication of the Joint Institute ions, passing through the for Nuclear Research. Dubna, micropores, which cause smallest E7-91-89(1991) measurable electro-chemical currents. 6. Danziger M., Nucl. Tracks Radiat. Meas., Vol.19, Nr 1-4, p.55 (1991) REFERENCES 7. Danziger M., JINR Rapid 1. Danziger M., Bernhardt A., Phys. Stat. Communications Nr 1 (58)-93 (1993) Sol. (b),1991,167, p.721 2. Danziger M., Bernhardt A., Phys. Stat. Sol. (b) 1992,164, p.569 PHYSICO-CHEMICAL CHANGES IN HEAVY IONS IRliADlATED POLYMER FOILS BY DIFFERENTIAL SCANNING CALORIMETRY

K.Cicśla, Ch.Trautmann*, E.F.Vansant**

Institute of Nuclear Chemistry and Technology, Warsaw, Poland. * Gesellschaft fur Schwerionenforsohung mbH, Darmstadt, F.R.G. ** University of Antwerp, Anlwerpen, Belgium.

irradiated polycarbonate (PC) and 1. INTRODUCTION polyimide (PI) films are also presented. Heavy ions irradiation induces 2. EXPERIMENTAL chemical and physical changes in thin polymer foils [1], Selective dissolution of 2.1. Materials and material in tracks leading to pores Poly(ethylenetherephtalate) 19 jum creation, is possible due to increment of thick foil Hostaphan, polycarbonate 30 reactivity of material in tracks in fim thick foil Makrofol and polyimide 25 comparison to polymer matrix material. tum thick foil Kapton were irradiated at Although methods of PTM production UNILAC accelerator in G.S.I., have been elaborated for some polymer Darmstadt. foils and influence of different factors on PETP foil was irradiated using Dy ions pore creation process have been with energy 13 MeV/u through a examined, little is known about the inner honey-comb structured mask having structure of latent tracks. transmission c.a. 90 %. The applied ion fiuence was about 5x10 ions/cm and 1 - The chemical as well as 5xl0n ions/cm . PC and PI foils weijg physico-chemical methods have been irradiated using ion fiuence 5x10 applied in track structure studies [2 - 6]. ions/cm . The scission and cross-linking of polymer 2.2.Methods chains as well as new chemical species DSC measurements were carried out have been discovered. in nitrogen stream using Perkin Elmer At present we have applied differential heat flow DSC7 calorimeter installed in scanning calorimetry (DSC) in studies of University of Antwerp. Measurements physico-chemical changes occurring after were performed with heating rate 2 and heavy ion irradiation in thin polymer film. 3°C/min for PETP foils and with 10°C/min The results obtained for and 3°C/min for PC and PI foils. poly(ethylenetherephtalate) (PETP) are WAXS measurements were performed presented and related to structural using X-ray powder Diffractometer changes confirmed by wide angle X-ray HZG4-C. The CUK« (Ni filtered) scattering (WAXS). Some preliminary radiation was employed. The DSC results obtained for heavy ions measurements were carried out in the Fig. 1. Normalized DSC curves of 19 /iw thick PETP foil Fig. 2. X-ray scat;ering curves recorded for PETP 19 ,

3.1. Poly(ethylenetherephtalate) arca DSC curves recorded for 19 thick curve\ I II III PETP foil: initial and irradiated with 13 1 59 5 132 MeV/u Dy ions using two different ion 2 52 13 140 fluences are shown in Fig.l. These curves 3 21 63 176 are normalized to 1. In the case of an initial sample, single The structural examinations of PETP endothermal effect of PETP melting with foils were carried out by the WAXS maximum at 261°C has been recorded method. The measurements were (curve 1). In the case of irradiated performed for initial PETP and for samples (curves 2, 3) an additional broad product irradiated with heavy ions using endotherm appeared in the temperature fiuence 1- 5x 1011 ions/cnT). range below the melting temperature Diffractograms are presented in Fig. 2. characteristic for the initial PETP. This Due to orientation of biaxially stretched endotherm is connected with the film, only few reflections are recorded. jremeltingof poly(ethylenetherephtalate) Only the (100) reflection (20 c.a. 26.0°) 7,8]. The premeiting effect is related to shows very high intensity. In diffractogram the presence of disordered phase in of irradiated sample the intensity of the PETP. It became more distinct while very strong (100) reflection is smaller in PETP foil was irradiated with Jarger ions absolute units but the background fiuence of 1 - 5 x 10 ions/cm (curve 3). intensity is relatively higher as compared Simultaneously heat of fusion associated to the diffractogram of the unirradiated with the main melting effect became foil. The absolute intensity of the (100) smaller. For foil irradiated with large ions reflection measured for irradiated fiuence the maximum of melting product is equal to about 2/3 of that endotherm was observed at lower measured for initial foil under the same temperatures (257°C as compared to Ó conditions (Fig. 2). The attenuation of 261 C for unirradiated foil). The results sample ordering occurring after heavy indicated on diminution of the crystalline ions irradiation can be concluded on the phase content after irradiation. basis of the above results. Three areas can be distinquished in 3.2. Poly(imide) and poly(carbonate) DSC curves. They are displayed in Fig. 2, The results obtained for PC and PI (curve 2). For results presented in Fig. 1 films are presented in Figs. 3,4,5. Physico-chemical changes in. 33

Fig. 3, DSC curves of 30 ftm PC foil Makrofol recorded with Fig. 4. DSC curves of 25 fim thick PI Kapton film recorded a heating rate 10 °/mln: initial (curve 1) and irradiated (curve 2) with a heating rate 10 °/min: initial (curve 1) and irradiated (curve 2); both products after heating to 500 °C with a rate of3°/min

The differences can be observed in The degradation effect was not slope of DSC curves of both PC and PI observed for PI Kapton foil heated to recorded for unirradiated and irradiated 680°C with 10 °/min (Fig 4). However, foils. The slope of DSC curves recorded while PI Kapton foil was heated to 500°C for the same sample was dependent on with a small rate 3 °/min a broad the heating rate (10 °/min or 3 °/min). exothermal effect was noticed in the The decomposition of iradiated PC foil temperature range from 364°C to 480 C Makrofol starts at lower temperatures in (Fig.5). The exotherm was larger for comparison to the initial foil (Fig. 3). The irradiated foil than for the initial one. The beginning of decomposition was observed heat involved during this transformation at 430°C for initial PC foil but at 360°C is equal to 46 kJ/g for the initial foil and for irradiated sample both heated 245 J/g for the irradiated foil. 10°/min. 3. D. Albrecht, P. Armbruster, R. Spnhr, 4. CONCLUSION "Investigations of heavy ion produced The differences in DSC traces of defect structures in insulators by unirradiated and heavy ions irradiated small-angle scattering", Appl. Phys. A. polymer foils are brought about by 37. 37-46 (1985). changes in film ordering resulting from 4. P.Yu.Apel, L.I.Kr avec, "Destruction of heavy ion irradiation. In the case of poly(ethylenetherephtalate) under biaxially oriented PETP film the irradiation with high energy heavy attenuation in film ordering was found by ions. Creation and concentration of DSC and WAXS methods. In the case of carboxyl groups in tracks", Khim. Vys. PC and PI film a decrease of thermal Energ., 25, No 2,138 - 143 (1991). resistivity was found by DSC method. 5. A.I.Vilenskij, V.A. Olejnikov, B.I. The work was sponsored in the frame Mchediishwili, A.B. Vnsiliev, P.Yu. of KBN grant 7 0233 91 01 and EEC grant Ape], "Structural changes in ERB 3510 pi 92 2372. poly(ethylenetherephtalate) during Acknowledgments PTM production", Khim. Vys. Energ. The authors would like to acknowledge 26, No 1,59- 62, (1992) Mrs. Miranda Hoof from Laboratory of 6. E. Ferain, R. Legras "Heavy ions Inorganic Chemistry University of tracks in polycarbonate. Comparison Antwerp for her help in performing the with a heavy ion irradiated model measurements. compound (diphenyl carbonate)", Nucl. Instr. and Meth. in Phys. Res. B, REFERENCES 82 (1993) 539 -548. 7. B. Ke, "Newer methods of polymer 1. Fleischer R.L., Price P.B., Walker characterization", New York 1964, R.M., Nuclear Tracks in Solids: 389. Principles and Applications, University 8. M. V. S. Rao, Ray Kumar, N. E. of California, Press. Berkeley (1975). Dweltz, "Studies on the structural 2. B.E. Fischer, R. Spohr, "Production dependence of melting behaviour of and use of nuclear tracks: imprinting poly(ethylenetherephtalate) by structure on solids", Rev. Mod. Phys., differential scanning calorimetry", J. 55, 931 - 933, (1983). Appl. Polym. Sci. 32, 4439 - 4451, (1986). RADIATION-INDUCED GRAFTING ONTO PETP TRACK MEMBRANES AND SOME NEW PROPERTIES OF MODIFIED MEMBRANES

N.I. Zhitariuk

Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research Dubna, PO Box 79,101000 Moscow, Russia

by poly-N-vinylpyrrolidone [3]) have been 1. INTRODUCTION made. Track membranes are produced by 2. METHODS physico-chemical treatment of polymeric In this paper a review of our films exposed to heavy ion beams. The selected dissolution of destroyed material experimental works on modification of converts the original film into a micro- PETP track membranes is presented. The and ultrafiltration membrane with radiation-induced grafting of monomers cylindrical through pores. Track from liquid phase has been chosen as a membranes prepared from poly(ethylene method for modification. Two methods of terephthalate) (PETP) film have a irradiation and post-irradiation treatment number of advantages which are have been used: associated with low thickness of a) pre-irradiation in air (MPA) membrane at high strength, high followed by grafting in vacuum or in argon uniformity of pore size, low content of atmosphere; extractable substances [1]. At the same b) pre-irradiation in vacuum (MPV) time track membranes made from PETP followed by grafting in vacuum without have such disadvantages as low chemical contact with air. resistance against alkaline medium, high Membranes have been exposed to electrostatic charge on the surface, high gamma-rays from Cs. contact angle at wetting with water, only The form of curves of grafting yield of short-term retention in pores the polystyrene (PS) vs. reaction time extragent solutions in organic solvents indicates that the rate of grafting process having low values of parameters, and the limiting grafting vield increases in and in many cases low water flow rate. the range: 0.1-F, 1-F, L-10 (where 0.1-F Therefore, the attempts to obtain track and 1-F are track membranes with pore membranes on the basis of films modified size 0.1 fim and 1 p, respectively, and by radiation induced grafting [2] as well as with constant porosity of about 8 %; L-10 to change surface properties of finished is a Lavsan film which was the matrix for membranes (for example, standard preparing track membranes). The change Nuclepore membranes have been covered of monomer sorption rate is identical to that of the grafting rate. However, as was irradiated samples will affect the grafting shown in [4,5] the grafting reaction rate. It was found that such influence proceeds at 70°C and at higher takes place in fact [8]. For MPV, the temperatures in kinetic range and is not storage of irradiated samples in vacuum limited by monomer sorption. This is at the room temperature increases their evidenced by the values of characteristic activities in initiation of grafting reaction parameter of grafting a. The overall until the storage time was longer than 100 activation energy of graft polymerization - 200 hrs. But for MPA, the activity of of styrene has sharp drop as the reaction irradiated samples continuously temperature raises. But it changes decreases. This decrease is more negligibly when pore diameters changes pronounced for samples stored in air than from small to big ones and further during in vacuum. transition from membranes to PETP films of different thickness. A limiting grafting From the obtained data the cunclusion yield has a maximum as temperature about probable nature of the initiating rises. The maximum coincides with the radical centres can be drawn. For MPV, -transition temperature of PETP the centres of grafting initiation are swelled in monomer [6]. A critical radicals. For MPA, on the first stage of thickness of membrane or film matrix, grafting the radicals, which migrate from which is defined as that thickness above crystalline phase of PETP to amorphous which the grafting rate per unit surface one, are initiating centres. As reaction area becomes constant or decreases, time increases, the oxyradicals obtained changes with the temperature with at the thermal decomposition of the activation energy close to activation peroxydes begin to take part in the energy of grafting (150 kJ/mole in the initiation of grafting. It is possible that for range 40 - 70°C and 25 kJ/mole in the MPA both types of radicals initiate range 70 - 100°C)[5]. Experimental value grafting at the same time. However, the of critical thickness of membranes and kinetic rate constants are essentially films (5^m at 70°C) satisfactorily different for radicals and oxyradicals [4]. coincides with the calculated one [7]. Investigation of structure of modified As far as the radiation-induced graft track membranes leads to a conclusion polymerization onto track membranes has that grafted polymer chains distribute in been carried out by preirradiation the bulk of membrane [9]. At electron methods we had expected that the time microscopic investigation we observed and atmosphere of storage of the formation of hills in spaces between pores which may be a possible consequence of

100

40 60 . Crofting yield (per centj

Microcovity size (urn) Fig. 2. Relative thickness of film L-10 Fig. 1. Distribution curves for specific surface arsa of microcavities for original 91) and and track membranes 1-F and 0.1-F grafted with PS (2) track membranes vs. grafting yield of PS Radiation-inductd grafting. 37 gel-effect at grafting [10J. As pore Micrornejitic:* pore sizer-9310 mercuric diameter increases (at constant porosity porometer. The specific surface area of membrane) the pores are clogged up in versus pore diameter was obtained a less degree by grafted PS. There are the proceeding from the cylindrical pore critical grafting yield of PS for each model. According to [15], the pore membrane with a definite pore size at surface and volume distribution of exceeding of which the effective pore Nuclepore membranes (trade mark of diameter sharply decreases. Costar Corp. (USA)) obtained by the Swelling in organic solvents and water mercury penetration method is in good changes as the chains of grafted polymer agreement with electron microscopy "data are incorporated in the bulk of in the pore diameter range from 0.015 fim membrane. The flow rate of liquid across to 5 «rn in spite of hysteresis at high the membrane depends both on the pressures. wettability of its surface by liquid As a result of a difference between the penetrating through the pores and on its etching rate of amorphous and crystalline swelling in the same liquid [11]. So, the regions of PETP [16] there is a improvement of membrane wettability by microporous structure on the membrane organic solvents by means of PS grafting surface and pore walls. The size of the leads to raising of stability of impregnated microcavities approaches that of partitions during membrane extraction crystallites that is about 10 nm or less. srocess [12]. Grafting of such polymer as 3 The curve of the specific surface S permits also to increase the stability of distribution for unmodified membrane the membrane being influenced by shown in Fig. 1 (curve 1) indicates that alkaline solutions [13]. This extends the track membrane has the large number of application range of track membranes microcavities of similar size (10 nm). The made of PETP. specific surface area of graft membrane (curve 2) is lower in the pore region 10 3. EXPERIMENTAL nm than that for original membrane 0.1-F Properties of the grafted membranes which served as a matrix for grafting. have been investigated. Composite or Apparently, the microcavities are filled graft membranes are a relatively novel with grafted polymer. type of polymeric membranes. The Fig. 2 can also be explained by necessity of their preparation arises from accomodation of grafted polymer in the the demands which are brought to microcavities which have been formed on semipermeable partition: chemical membranes with different pore sizes and stability in separated media, high pore numbers as compared with the mechanical strength at minimum original (unetched) film. As can be seen, thickness as well as high selectivity with the change of the relative thickness gain respect to components of separated of the sample during accumulation of medium at the maximum rate of mass grafted PS decreases in the range: L-10, transfer. 1-F, 0.1-F, that is as distance between the Obviously, many of the demands are pores decreases and hence because of mutually exclusive ones. Therefore, the increasing surface area. In this case, the selection of the suitable membrane for a part of grafted polymer which given separation process is essentially the accomodates in the microcavities will search of the most optimum compromise increases in the same sequence. Thus, for between its properties. For example, gas grafting performed by both methods separation membrane prepared from (preirradiation in vacuum and in air), polyvinyl pyridine possesses excellent when grafted chains distribute not only on selectivity with respect to a mixture of N2 the surface but also in the bulk of - O2 and adequate permeability but it is membrane matrix, grafted polymer fills, characterized by a very low mechanical in the first place, the microcavities which strength [14]. have a size near to that of crystallites of The specific surface area of track PETP. It is interesting to note that membranes was measured on a grafting by both methods changes the Fig. 3. Relative gas permeability for graft membranes with constant porosity as compared with that for original ones vs. grafting yield of PS

Grafting yield (per cent)

Fig. 4. Relative gas permeability for graft membranes with constant pore donsity as compared with that for original ones vs. grafting yield of PS

fT 12 1'6 Grofting yield (per cent)

\0-t •t&&&$ 0.2-F-modified 0.05-F-modified

Fig. 5. Relative water flow rate vs. grafting yield of hydrophilic polymer

X'O 2.0 4-.0 6.0 8.0 Grafting Yield (per cent) thickness of film in a less degree than that for membranes both with different pore in the case of surface distribution of sizes and between pore distances under grafted polymeric chains (for example, the condition of constant porosity equal to during polymerization onto active sites 8 - 9% (Fig.3), and with different porosity, formed during thermooxidation of PETP that is when membranes have constant [17]. pore density but different pore diameter During graft polymerization pore size (Fig. 4). In the first case (Fig. 3) the of membrane is expected to change. The relative gas permeability changes effect of pore clogging was investigated negligibly at low grafting yields. This Radiation-induced grafting 39 range of grafting yields depends on the yield for surface modification of track pore size of membrane substrate and it membrane to reach maximum water flow expends as pore size increases. rate. Subsequently, as the grafting yield REFERENCES increases, there is a sharp drop of gas 1. Nuclear Track Membranes. permeability (with the exception of Compilers: V.I.Kuznetsov, membrane 1-F-gr-PS for which a drop of P.Yu.Apel, Dubna, 1989. gas permeability takes place at a higher 2. Brevet d'invention 2.181.215, France. grafting yield, i.e. more than 60%). Since Int. cl. C 08 j 1/00//B 01 d 13/00,1973. there is a linear relation between membrane thickness growth during ?. lite Science. Filtration Catalog. grafting and grafting yield (look above Costar Corp., 1992 and in [18]) it may be supposed that a 4. N.I.Zhitariuk, P.AZagorets, sharp drop of gas permeability occurs V.I.Kuznetsov. Khimia Visokih because of pore size decreases. The Energiy, 1990, V.24, P.314 (in obtained dependencies suggest that at a Russian). low grafting yield the effect of membrane 5. N.I.Zhitariuk, N.I.Shtanko. Polymer, surface modification can be reached 1991, V.32, P.2406. 6. N.I.Zhitariuk, without pronounced reduction of pore V.I.Kuznetsov,P.A.Zagorets. size. Makromol. Chem., Rapid Commun., 1989. V.10. P. 613. 4. CONCLUSIONS 7. N.I.Zhitariuk, P.A.Zagorets, As follows from Fig.3 and 4 the V.I.Kuznetsov. J. Appl. Polym. Sci., character of pore clogging is 1990, V.40, P.1971. approximately identical for membranes 8. N.I.Zhitariuk and N.I.Shtanko. Eur. with large pores [1-F(6xl(r) and Polym. J. 1990, V.26, P.847. 1.5-F(6xlO )]. But when we compare the 9. N.I.Zhitariuk et al. Preprint JINR curves of the relative gas permeability for b 18-88-538, Dubna, JINR, 1988. 0.1-F and 0.05-F(6xlO ) it can be seen 10. N.I.Zhitariuk. N.I.Shtanko. Commun. that the character of gas permeability JINR 18-88-548, Dubna, JINR, 1988. reduction changes depending on the 11. N.I.Zhitariuk, V.I.Kuznetsov, average distance between the pores L\ at N.I.Shtanko. Preprint JINR, low L (0.6 /urn against 4.8 /*m) clogging of 18-88-537, Dubna, JINR, 1988. pores intensifies as the grafting yield reaches ~ 7%. Thus, during grafting of 12. P.Yu.Apel et al. Proc. Intern. Symp. PS the pores of nuclear membranes are Membranes and Membrane clogged by grafted polymer to a greater Separation processes, Sept. 11-15, degree when their original diameter is 1989. Toruń, Poland, 1989. smaller and their number per unit 13. V. M. Kochkodan, M. T. Brik, B. V. surface area is larger. Mchedlishvili, N. I. Zhitariuk, Ukr. Khim. Zh. 1987, V.53, P.100 (in As is shown in Fig. 5 modification of Russian) membrane surface by hydrophilic monomer results in the growth of water 14. J. Y. Lai, S. L. Wei, J. Appl. Polym. flow rate up to 3 - 4 times for pore size 0.1 Sci. 1986,'V.32, P.5763 fim as compared with unmodified 15. A. A. Liabastre, C. Orr, J. Colloid membrane of the same pore size. The Interface Sci. 1978 V.64, P.l. relative water flow rate vs. grafting yield 16. Y. Komaki, T. Segushi, Polymer. 1982, goes through the maximum. At low V.23,1143. grafting yields the increase in the content 17. V.V.Korshak, D. Ya. Tsvrmkirj, S. P. of VPMI rises hydrophility of membrane Krukovski, Doki. Akad. Nawk 53SR. surface. However at higher grafting yields 1962, V.146, P.1347 (in Rumian). the process of membrane swelling results 18. N.I.Zhitariuk, V.I.Kuznetsov, in the decrease of pore size. Therefore N.I.Shtanko. Environm. Protect. Eng. there is the optimum value of grafting 1989, V.15, P.lll.

PARTICLE TRACK MEMBRANES AS MODELS FOR BIOLOGICAL ION CHANNELS

CA. Pasternak*, P.Y. Apel**, CL. Bashford*, D.T. Edmonds***,Y.E. Korchev*,****, A.A. Lev****, T.K. Rostovtseva*,****, and N.I. Zhitariuk**

*St George,s Hosp. Med. School (London University), **Joint Institute for Nuclear Research, Dubna, Russia, ***Clarendon Laboratory (Oxford University) and ****lnstitute of Cytology, St. Petersburg, (Russian Academy of Sciences)

Abstract, Particle track membranes composed of polycthylenctcrephthalate that have been etched to produce narrow pores show many of the properties of biological ion channels: rapid switching (quantal current flow), selectivity between cations and anions, and modulation by H+ and divalent cations such as Zn2+ and Ca2+. This has implications (or our understanding of ion channels, as well as opening up the possibility for designing new classes of ionic sensors.

had been etched with alkali were used. 1. INTRODUCTION The membranes were of 5 or 10 um Many of the features of endogenous thickness and had average pore sizes of ion channels (Hille, 1992), or of pores <20 nm diam. They were clamped induced across the plasma membrane of between two chambers containing susceptible cells by exogenous agents such buffered KC1 of various concentrations. as certain toxins, immune molecules or Unless the relative selectivity of such detergents (Pasternak et al 1992), are filters (for cations over anions) was being well-understood. However, the exact measured, the KC1 solution was of the mechanism by which such channels and same strength in each chamber (generaly pores oscillate between high-conducting 0.1M); when selectivity was being or "open", and low-conducting or "closed , measured, a gradient of KC1 (e.g.lM states is not clear. Nor is it known how versus 0.1M) was used. In either case, protons and divalent cations - often, of current was continuous with membranes relative efficacy H+ Zn2+ Ca2+ Mg2*- of pore size approx. 20 nm diam., but promote the low-conducting or "closed" oscillated between high and low state of endogenous ion channels or of conducting states when the pore size was exogenously-induced pores. The present around 2 nm diam. The nature of the results, obtained with particle track oscillations - which were in the time range membranes (Lev et al 1992, 1993; of seconds - were reminiscent of those Pasternak et al 1993), throw some light on seen in endogenous ion channels or toxin- this problem. induced pores, namely of "square wave" characteristic. Such similarity was 2. PARTICLE TRACK MEMBRANES SHOW surprising, since (a) the pores were FLUCTUATIONS BETWEEN HIGH-CONDUCTING AND approx. 1000 fold deeper (viz 5 or 10/tm) LOW-CONDUCTING STATES than those across biological or synthetic Particle track membranes composed of lipid membranes (viz approx. 5 nm) and polyethyleneterephthalate (PETP) that (b) the material was devoid of any 42 C. A. Pasternak ct al.

"mobile" molecules such as lipid or presence of alcohol or urea. Hence both protein, surface charge and hydrogen-bonded molecules such as water may contribute 3. PARTICLE TRACK MEMBRANES ARK SENSITIVE TO 1'ROTONSAND DIVALENT to the effect. CATIONS ACKNOWLEDGEMENTS When the medium in the chambers We are grateful to the Cell Surface separating a membrane of approx. pore Research Fund, Molecular & Cell size 2 nm diam. was altered by (i) Biology Network (MCBN) of UNESCO lowering the pH or (ii) adding divalent and The Wellcome Trust for financial cations (as chloride or sulphate), support. conductance was decreased. Raising pH, or chelating divalent cations with REFERENCES ethylenediamine tetra acetic acid Hille B. (1992), Ionic channels of (EDTA). reversed the effect. Inhibition excitable membranes. 2nd edn. by low pH or by divalent cations was not Sunderland,Massachusetts: Sinauer observed - or only slightly so - if Associates. membranes of approx. pore size 20 nm Lev, A.A., Korchev, Y.E.,Rostovtesa, were used. T.K., Bashford, C.L. & Pasternak, C.A. 4. CONCLUSION (1992), Lipid impregnated nuclear filters as a model for studies of surface These results, some of which have conductance and single channel been reported in greater detail elsewhere phenomena. In: Biophysics of membrane (Lev et al. 1992, 1993; Pasternak et al transport (ed. J. Kuczera & S. 1993) suggest that the properties of ion Przestalski), pp. 321-349. Agricultural flow through narrow pores in PETP University of Wroclaw, Poland. membranes resembles those through Lev, A.A., Korchev, Y.E.,Rostovtseva, endogenous ion channels and T.K., Bashford, C.L., Edmonds, D.T., & toxin-induced pores. We propose the Pasternak, C.A. (1993) Rapid switching of reason for this to be due to the special ion current in narrow pores: implications properties of ion flow along surfaces, for biological ion channels. Proc. R. Soc. irrespective of whether they are 252:187-192. composed of PETP, of lipid or of protein: Pasternak, C.A., Alder, G.M., if surfaces are close together, as in an Bashford, C.L.,Korchev, Y.E.,Pederzolli, endogenous ion channel, toxin-induced C & Rostovsteva, T.K.(1992) Membrane pore or narrow (2nm diam) PETP damage: common mechanisms of membrane, the special properties are induction and prevention. FEMS observed. Similar effects have been Microbiol. Immunol. 105:83-92. reported by others (Sachs + Feng Pasternak, C.A., Bashford, C.L., 1993a,b). If surfaces are separated by Korchev, Y.E., Rostovtseva, T.K. & "bulk" liquid, as in wider ( 20nm diam) Lev,A.A (1993). Modulation of surface PETP membranes, the properties of flow flow by divalent cations and protons. through the bulk liquid dominate, and the Colloids Surf. A 77:119-124. special properties are not observed. Sachs F & Feng Q.(1993a). Gated, The mechanism that renders such ion-selective channels observed without "surface flow" (a) discontinuous - i.e. membranes: novel properties of the oscillating between high-conducting and gigaseal. J. Physiol., Lond.459:P419 low-conducting states - and (b) sensitive Sachs F & Feng Q. (1993b). Gated, to protons and divalent cations appears to ion-selective channels observed with be related to the nature of the surface. patch pipettes in the absence of PETP track-etched membranes contain membranes: novel properties of a negative charges (carboxyl groups): when gigaseal. Biophys.J. 65:1101-1107. these are neutralized oscillations are reduced; they are also reduced in the PROPERTIES OF PETP TRACK MEMBRANES OF DIFFERENT THICKNESSES

P.YuApel, A.Yu.Didyk, I.E.Larionova, T.I.Mamonova, O.L.Orelovich, L.I.Samoilova, I.V.Yanina, N.I.Zhitariuk

Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Dubna, Russia

Abstract. The basic properties of polyethylene tercphthalatc (PETP) track membranes (TM) made of the films with the thicknesses of 10 and 20 jum arc investigated. The membranes with the pore diameters of 0.2, 0.4 and 1 ,um were chosen for comparative study. The porous structure of the membranes was characterized by the following set of parameters: pore density, pore size, bubble point, pore radius distribution measured by the Coulter porometer. The tensile strength, water and gas flow rate were determined for both types of the TMs. The filtration processes of liquid and gaseous media were investigated. Advantages and disadvantages of "thin" and "thick" TM are discussed.

accelerators. It gave us a possibility to 1. INTRODUCTION produce membranes with the thickness of For many years track membranes were 20 or even 30 ^m. Study of the properties produced of polymer films with the of these "thick" track membranes is of thickness of about 10 fim [1,2]. Several great practical interest. reasons caused the use of such thin material. First, fission fragments and 2.EXPERIMENTAL accelerated heavy ions with the energy of The samples of TM's were produced of 1 MeV/nucleon have rather short range. biaxially oriented PET films with nominal Heavy fraction of the fission fragments thicknesses of 10 and 20 ^m. The foil of does not penetrate PET layer of 15 ftm 10 fim thickness was irradiated by xenon thickness. Similarly, the range of 1 ions with the energy of 1 MeV/nucleon on MeV/nucleon xenon ions (the ions of this U-300 cyclotron. The irradiation of the kind were accelerated on the U-300 films with the thickness of 20 //m was cyclotron at FLNR JINR) is ca. 17 fim carried out by 3 MeV/nucleon krypton which sets an upper limit on the thickness ions on the U-400 cyclotron of FLNR. of the track membrane. Second, Since the mechanical strength of the according to theory the thicker is the thicker film is generally higher than that membrane, the lower are the of the thinner one the irradiation permeability and the rate of filtration conditions were chosen so as the track process. That is why many attempts were densities in the films of 20 ^m thickness done at the FLNR to manufacture TM were higher than in the films of 10 with the thickness of 3 or 5 jum. The thickness (in the following we denote samples of such membranes showed very them by TM20 and TM10, respectively). high initial flow rate but very short life Both films were subjected to ultraviolet time due to rapid plugging by particles to sensitization and subsequent chemical be separated. etching by alkali solutions m a usual way. Recently the beams of accelerated The porous stucture characteristics of heavy ions with the energy higher than 1 the TM samples were measured by a set Mev/nucleon have become available at of different methods. The pore density U-400 in Dubna and at some other and the size of openings on the surface 44 P, Yn. Apel ct al.

measurements were performed to find the valus of each parameter. In order to - THIO calculate pore diameters from the TH10 measured water (low rates given in the tables, Poiseuille flow through the pores was assumed [3]. The values of effective lilt pore diameters were also calculated from the gas flow data using an appropriate computer program. The close agreement ii ..V... Por* ttzC(fcM 01 of pore sizes obtained by these two means li VI demonstrates the validity of the VŁ P«r« tizal^^ 0.6 assumptions used for calculations. It is clearly seen from the data FIG. 1. DIFFERENTIAL (low distribution? (arbitrary units) as presented in Tables 1-3 that there is a functions of poro DIAMETER for the pairs of track mrmbrnnes difference in pore shape of TM'10 and with nominal pore size of 0.2, 0.4 and 1 pm (from loft to TM20. TM10ss have cylindrical pore right) channels whereas pores in TM20's are tapered. It shows that etch rate ratio in the process of TM20 production is smaller because the average energy loss rate of 3 were estimated by means of a scanning MeV/n Kr ions in the PET film is lower electron microscope (JSM-840, JEOL). than that of 1 MeV/n Xe ions. Another The bubble point was measured with the possible reason may be a lower efficiency use of ethanol as a wetting agent. The of oxidation process in tracks in thicker Coulter porometer II was used to film because of longer time of oxygen determine pore size distribution and the diffusion into the film matrix. In the SEM values of mean flow pore size in each picture (Fig. 2a) one can see the sample. The size factor was set equal to difference between the pore size on the 0.48 (wetting liquid: Porofil). The burst surface and in the depth of the membrane strength was determined at a differential of 20 fim thickness with the nominal pore pressure which breaks 1 cm unsupported diameter of 0.4 fim . In contrast to TM20, membrane sample. The air flow rate was there is almost no similar effect in case of measured by means of the Gilmont TM10 (see Fig. 2b). flowmeters (pressure drop of 0.1 bar, sample area of 1 cm ). The flow rate of TMlO's and TM20's have different pore destilled prefiltered water was measured channel shapes and lengths but for the samples of 50 mm in diameter (at nevertheless they are characterized by the differential pressure P of 0.2 up to 0.7 almost identical pore size distributions bar). The filtration performance of the measured by the porometer (Fig. 1). It TM's was tested with tap water under allows us to assume that the diameter of dead end conditions. Retention efficiency cylindrical pores in the TM10 is very close in the process of air filtration was to the diameter at the interior of tapered measured using laser particle counter channels in the TM20 with the same MET-ONE type A2120. nominal pore size. For comparative study we have In spite of higher porosity the thicker selected from a number of TM20's the membranes show tensile strength about 10 samples with the bubble points and mean per cent higher. It gives a significant flow pore (MFP) sizes as close as possible advantage to TM20's. to the corresponding parameters of the Water and air flow rates for TM20's TMlO's. The differential flow distributions exceed those for TMlO's although measured by the Coulter porometer for increasing thickness must have led to three pairs of TM's are shown in Fig. 1. decreasing throughput. Obviously, the conical shape of pore channels and higher 3. RESU'.TS AND DISCUSSION pore density of the TM20's compensate The parameters of the membranes are the influence of membrane thickness. summarized in Tables 1-3. At least three Filtration throughput of tap water for Fig. 2. SEM photographs of the surfaces and the edges of TM's broken In liquid nitrogen, a: thickness I = 10//m, nominal pore size d=0.2/*m; b: I =20 ftm; d=0.2«m; c: I =10/*m, d=0.4^m; d: I =20 ftm, d=0.4/tm; e: I =10/

"204ó" '6080100 \i0 140 T?0 nilrotiOPi limu (mtn)

6080 T'ftb 'i'io 18D R'll'otion lim'1 ' TiinJ

Fig. 3, The filtration throughput of tap wa'.er for the membranes with nominal pore sizes of 0.2 ftm (a),, 0.4 ftm (b) and 1 ftm (c). The membrane thicknesses are 20^m (1) and 10 fim (2). The inlet pressure is 0.8 bar

intersections increases with increasing thickness of the membrane. Fig. 4 illustrates the real porous structure of two membranes having 0.2 fim pores and the thicknesses of 10 and 20 /xm. In the process of filtration some pores can be plugged by particles. In Fig. 4 is shown the situation when only one pore left open. The plugged pores which intersect open one participate in the total flux of Fig. 4. The cross sections of TM10 and TM20 with the pore the liquid through the membrane. The diameter of O.^m and pore density of ca. 3x108 cm. A!) but one of the pores are plugged by particles in the filtration thicker the membrane, the greater process. The water stream is shown in black, (a) TM10: 21 number of pores are involved in the per cent of the total pore lenght and 6 pores share in the filtration process. This could be the water flow, (b) TM20: 43 per cent of the total pore lenght and reason why increasing thickness does not 12 pores share in th water flow reduce the filtration rate as it could be expected from the Poiseuille's law. If the intersections in the membrane matrix. It proposed model is valid one can draw a should be noted that effects of pore conclusion that inclined pore channels intersections appear only if the porosity is are very important for improvement of high enough. In general, the angle TM's properties as they provide many distribution, the foil thickness to pore size ratio and number of pores define, to say, /•'iffrufi'm o/ air through track mcmprmifs i-n.«i-i iwlu:lr i.uunli.r MI.T UNK I'clH'll'lllllMI IIT I'L/lil'lc'fl Ul nil' VflilMit.V V i:iu/s "i:rirflVir Ml, IT 02 II 3-1 MM Ic-h I Fig. 5. Penetration of particles as « function of particle size, poro diameter and membrane thickness for ambient air IL-.1, filtration

lo-l , IC-Si

le-O;

lK-7; 'l, 10 Mil' size Is O.^.i) >tin MM Hi/.c is ll.Ub urn .-Itji* Il TM'i lliirldli^ In Jim '

Table 1. Parameters of track membranes withtho nominal pore size of 0.2/

TM10 TM20

Thickness, fum 9.9 20.0 Pore diameter obtained by SEM, fim 0.25 0.30 Pore density, cm"2 3.2xl08 3.8x10s Mean flow pore diameter, fim 0.198 0.205 Bubble point, bar 2.8 3.0 Burst strenght, bar 2.0 2.2 Air flow rate, 1/h cm2 20 22 Air flow effective pore diameter, /

Table 2. Parameters of track membranes with the nominal pore size of 0.4,nm

TM10 TM20

Thickness, fim. 9.0 18.5 Pore diameter obtained by SEM, fim 0.40 0.65 Pore density, cm"2 1.2x10s Mean flow pore diameter,/

Table 3. Parameters of track membranes with the nominal pore of 1 ftm

TM10 TM20

Thickness, fim. 9.0 18.0 Pore diameter obtained by SEM, jum 0.85 1.0 Pore density, cm'2 1.2xl07 2.0xl07 Mean flow pore diameter, fim 0.83 0.91 Bubble point, bar 0.72 0.72 Burst strenght, bar not measured not measured Air flow rate, 1/h cm" 75 95 Air flow effective pore diameter, fim 0.81 0.83 Water flow rate, ml/min cm2 (P=0.2 bar) 19 20 Poiseuille pore diameter, fcm 0.92 0.89

Probably, under such conditions not only to expectation, the initial flow rate different pore length but different pore characteristics of thicker TM's are found shape can also contribute to higher to be not worse than those of thin retention efficiency of thicker membranes. The membranes with the membranes. thickness of 20 show higher tensile strength even at higher porosities. 4. CONCLUSIONS Moreover, performing tap water filtration The track membranes of two different by the thicker membranes of high porosity thicknesses (10 and 20 firn) were we observed the improved throughput compared using different tests. Contrary which is assumed to be caused by the formation of the unified system of pores. 2. Flerov G.N., Vestnik Akademii Nauk It enables us to conclude that TM's with SSSR, 1984, No.4, 35-48. the thickness of 20 //m are a very 3. Beck R.E. and Schultz J.S., Biochim. promising product. Biophys. Acta, 1972, 255, 273. 4. Spurny K.R., Environmental and REFERENCES biological disperse system. In "Physical 1. Ballew H.W., Basics of filtration and and Chemical Characterization of separation. Pleasanton. California, Individual Airborne Particles", Ed. by 1978, p.8. K.R.Spurny, ELLIS HORWOODLtd.,

ELECTRON MICROSCOPY INVESTIGATION OF SHAPE AND CLOGGING OF TRACK MEMBRANE PORES

O.L.Orelovich, V.AAltynov, P.Yu.Apel, A.Fiderkiewicz*, T.I.Mamonova, I.V.Yanina, N.I.Zhitariuk

Joint institute for Nuclear Research, Dubna, 141980 Russia institute of Nuclear Chemistry and Technology, Warsaw, Poland

Abstract. Some procedures of sample preparation for scanning electron microscope (SEM) studies of track membranes are described. Both porous structure parameters and the behavior of the membranes in filtration processes can be investigated using the methods of SEM. Examples of examination of the membranes used for filtration in different modes are given.

occuring during the freeze-fracturing 1. LIQUID-NITROGEN process [2], The deformation of thin FREEZE-FRACTURING METHOD partitions between neighbouring pores is This method is well-known and clearly seen in the membrane as shown in described in many works [1,2,3]. Usually, Fig. 1. As a result, the measurement of polymer materials are disposed and pore diameter in the depth of the foil is fractured in liquid nitrogen. The new impossible. In order to avoid this difficulty surfaces freed by this procedure are we use some specific properties of the coated with gold and examined by SEM. polymeric films used for track membrane But the accuracy of this method is limited (TM) production. because of the plastic deformation Biaxially oriented foils such as

Fig. 1. Scanning electron micrograph of the surface and the edge of a liquid-nitrogen freeze-fractured PETP membrane. Fig. 2. Picture of steps in the bulk of a PETP membrane Deformation of partlon walls is obvious. As a result the size (see text) of pores in the middle of the bulk is larger than pore diameter on the surface of the membrane ' * '•Mi.

Fig. 3. Section of a broken PP membrane after gamma ray Fig. 4. The edge and the surface of broken PETP irradiation membrane after gamma ray irradiation polypropylene (PP) or poly(ethylene were irradiated by gamma rays. In this terephthalate) (PETP) films have foliated case the degradation of the polymer structure which can be developed in the occured and the membrane became more process of fracturing. Due to that we can brittle. If PP was preirradiated the use of distinguish several layers like steps on the liquid nitrogen is not needed and the edge of the broken membrane. It makes membrane can be broken with tweezers possible to measure the size of pore only. Picture in Fig.3. shows relevant channels at different distances from the porous structure. Because the membrane surface. An example of such a structure is got brittle after gamma ray exposure the presented in Fig. 2. Measurements deformations were essentially smaller and performed in each of these steps allows quantitative analysis of the picture one to determine the change of the value obtained is possible. The pore shape in of pore size along the pore channel. this membrane is like a sandglass. This Using such technique one can estimate result is an agreement with the shape of tapered holes. In case of measurements performed by other conical channels we obtain the values of methods. Using this procedure one pore size in the bulk of membranes some should take into account that at very high of which are in agreement with those doses many polymers can undergo strong found by other methods (for example, gas damage accompanied by accumulation of flow measurements, bubble point, etc.). defects on the surfaces, cracking, etc. Further, in order to improve the That is why one should find a sample preparation procedure we have compromise between brittleness and tried to suppress deformation by reducing retaining original structure. For instance plasticity. With this aim the membranes in case of PP it occurs at a dose of ca. 50

Fig.5. Micrograph of the TM surface after filtration of 181 tap Fig. 6. Reciprocal flux vs. total filtrate volume for dead-end water with a cross-flow method (1) and cross flow (2) filtration. Arrows show the moments of addition of new portions of water into filter holder. Inlet pressure is 0.4 bar Electron microscopy., 53

Fig. 7a. X-ray spectra of particles collected onto surface of Fig. 7b. Micrograph of particles trapped by the track TM after silane filtration. It was obtained with the LINK membrane in the filtration of the silane Systems EDS 860-serie

kGy. Similarly, Fig. 4. illustrates the filtration kinetics and SEM observation of absence of partition wall distortion in the membrane surface lead to identical PETP membrane after gamma ray conclusions about the mechanism of irradiation and subsequent fracturing. separation process. Quantitative and qualitative analysis of 2. STUDY OF WATER AND GAS particle composition is possible using FILTRATION ACROSS TRACK MEMBRANES X-ray microprobe analysis. For this work we used energy dispersive spectrometer Track membranes are very convenient (EDS). The next example illustrates the for SEM investigation of particulates use or this device to find out the origin of collected on their surfaces in the contaminations in silicon single crystals processes of dead-end and cross-flow growing from gaseous silane (S1H4). An filtration [4]. Using such advantages of X-ray spectrum and a micrograph of TMs as smooth surface and narrow pore particles trapped by a TM during size distribution it was obtained almost filtration of the silane are presented in clean surface in a cross flow filtration of Fig. 7. In this picture one can see the tap water. In our opinion, such results needle-like particles. The treatment of have been obtained due to also high cross the spectrum showed the presence of Ti flow rate of water stream along a in the particles. A possible source of such membrane surface (more than 5 m/s). particles is the corrosion of stainless steel One can see from the micrograph in Fig. tubes through which the silane moves to 5 and from comparison of the curves for the reactor. The corrosion products dead-end and cross flow microfiltration penetrating into the crystals reduce the presented in Fig. 6 that only bulk clogging quality of the semiconductor. of pores with particles having the sizes considerably smaller than the pore diameter takes place. There is no 3. CONCLUSION superficial clogging with cake formation Methods of sample preparation and during cross flow filtration. According to SEM investigation of the samples bring modified Darcy's equation, filtration, into accordance a number of different accompanied by cake formation, gives a measurements of TM pore shape. It was straight line in the coordinates reciprocal shown by SEM and mathematical of flux vs. filtrate volume (see line 1 in methods that inner clogging of pores is Fig. 6) [5]. Therefore, the analysis of the main reason of a flow rate decrease 54 O, L. Orelovicli ct al. during cross flow filtration of tap water 3. Orelovich O.I..., Methods of electron across the TM. Application of SEM with microscopy used for studying nuclear EDS has made possible to define the membranes. In: Proc. Intern. composition of the solid contaminations Workshop on Track Membranes, which bring to deterioration of single Warsaw/Katowice, 1990, pp.74-77. crystal silicone used in microelectronics. 4. X-Ray fluorescence analysis of environmental samples. Ed. by REFERENCES Thomas G. Dzubay. Ann Arbor 'J. Goldstein J.I., Yakowitz H., Practical Science Publishers Inc., 1977. scanning electron microscopy, Plenum 5. Porter M.C., Membrane Filtration. In Press, New York and London, 1975 Handbook Sep. Techn. Chern, Eng. 2. Hopfe J., Rauschenbach B., Scanning Ed. by P.A.Schweitzer, 1978, pp. electron microscope investigations of 2/3-2/103. nuclear pore filters in polyester foils. Nucl. Tracks, Vol 4, pp. 161-169,1981 COMPUTER SIMULATION OF TRACK MEMBRANES PORES OVERLAP

V.A. Oleinikov

Institute of Crystallography Russian Academy of Sciences 117333, Moscow, Leninsky Pr,,59, Russia.

pores orientation allows to decrease 1. INTRODUCTION pores overlap probability. It is true, One of the main advantages of track because a pore overlapped by another membranes (TM) is their great selectivity one in one cross-section may be single in defined by pores size uniformity and another cross-section. This pore do not pores forms perfection [1,2], Different decrease track membrane selectivity. pores should not be overlapped and The double overlaps is the case when should not form multiple holes for in any membrane cross-section there will creating these membranes. It limits be found a pore for a given pore, so as the membranes porosity and, therefore, their distances between their axis are less then penetrability. Process of track their diameters. These defects of double membranes making includes initial matrix overlaps form slit pores which give rise to exposed to high energy ions beam. It changes in selectivity for planar rigid causes stochastic pores distribution and particles only (for example disk form). impossibility for regular pores structure In the case of triple overlaps for one creation. Thus overlaps of pores are pore there will be found another two inevitable and it is necessary to minimize pores so as the conditions of double formatting of these overlaps on the way overlaps are satisfied for each pair. Thus, of new type of track membranes triple overlaps defects and multiple development. overlaps defects form pores with larger For the first time the problem of effective diameters. double and multiple cylindrical pores Therefore both double overlaps pores overlapping was studied in 1977 [3]. In probability and multiple (multiplicity 1979 similar problem for quadratic shape equal and more than 3) overlaps pores pores was solved [4]. In both works track probability are necessary for track membranes in which parallel pores membranes characterization. system was made by exposing it to the parallel beam of ions was investigated. 2. TRACK MEMBRANE MODEL Later it was shown in the Laboratory of For calculation of pores overlaps Nuclear Reaction (JINR, Russia, Dubna) probability some membrane area with and then in [5], that the divergence of defined pores distribution in co-ordinates and directions is investigated. For each tilt A. This parameter is defined as pore placed in this area a checking on dimensionless projection of pore axis on double overlaps is made. If this condition membrane surface: is satisfied a checking on triple overlaps is accomplished also. This checking is A = 1 • tga • VN (2) made for defined number k of membrane cross-section. Apparently it takes the more of computer time the more number Where: 1 - membrane thickness, a - tilt of pores n are taken into account. On the angle of pore axis to membrane surface other hand decreasing of n makes model normal. Nomogram showing the of pore system more regular and thus relationship between parameter A, angle makes the model less correct. a and surface density of pores N for 10 To obtain correct results with jum thickness TM is given in Fig. 1. acceptable time of calculation initial Number of pores on investigated area pores co-ordinates are defined with using was 100-1000, the co-ordinates of 10-104 Monte-Carlo method on large area. Then pores were taken into account. The some part of this area is considered. This number of cross-sections, in which pores approach allows only the pores belonging overlaps were tested, was k = 5 - 20 . to a considered area in some cross-section to be taken into account. Thus the 4. RESULTS AND DISCUSSION number of pores in considered area is Dependencies of double W2 and triple defined by Monte-Carlo method. W3 overlapping probabilities upon Really studied factor is the membranes porosity P are shown in Fig. 2 dependence of pores overlaps probability and Fig. 3. The dependencies |are on the type of pores direction presented in co-ordinates of nominal distribution. Tree types of distribution porosity Pn, effective porosity Peff, and were investigated in present work: dimensionless diameter of pores %. The 1. All pores are disposed in one plane. nominal porosity is ratio of total pores Pores are distributed randomly uniformly area to membrane area, in this case pores in the interval (-ao

60 W Pijft%)

too m p»(%) Fig. 1. Nomogram connecting a — angle of pores till with the Fig. 2. Dependencies of double W2 and triple W3 normal, N — surface density of pores, and parameter A overlapping probabilities upon nominal porosity Pn, effoctive porosity Peff, and dimenslonless dlamBter of pores X for track membrane with parallel pores

0,2 dl 05 0.1 1,0 W -I—L—I R- 20 30 tO SO 60 W Peff(%) Fig. 3. Dependencies of double W2 and i.o I -' , -| triple W3 overlapping probabilities upon nominal porosity P3, effective porosity Peff, ; f* """" r o,s %. and dimenslonless diameter of pores % f° track membrane with non-parallel pores. Parameter of pores axis tilt Is D = 0.01 fi 0,6 \ 1 — random-uniform in one plane; z 2 — random-uniform in two planes; OA ł 3 — random-uniform in a circle f i'i 0 M Ć'm so eo too nsp

(parallel pores). used the probabilities are W2 < 1% for % For small porosity, pores overlap s 0.34 (effective porosity Peff. = 9%) and probabilities for the second and the third W3 < 1% forx < 0.65 (PCff. = 28%). variants of pores angle distributions (in two planes) are approximately equivalent. 5. CONCLUSION The pores overlap probability for the first Numerical model for estimation of the variant (distribution in one plane) is double pores overlaps (slit pores) larger. In the case of large value of probability and the triple pores overlaps porosity the difference between the probability was developed for the case of second and the third variants distributions track membranes with non-parallel pores appears. system. For all considered variants the smaller Three methods of pores directions values of pores overlap probabilities | are distribution were investigated: realised when random distribution of 1) random-uniform in one plane; pores direction in two planes is used. 2) random-uniform in two planes; When large value of parameter 3) random-uniform in a circle. characterizing pores axis tilt A = 0.1 is The last two methods are approximate equivalent, but give less values of pores 3. Barashenkov B.S., Nuclear filters overlaps probabilities in comparison with pores dispersion, JINR Preprint tbe first method. R14-10532, Dubna, Russia. Using large angles of pores axis with 4. Riedel C, Spohr R., Statistical the normal gave the possibility to properties of etching nuclear tracks. I. decrease pores overlaps probabilities. In Analytical theory and computer particular, when A = 0.1 is used the simulation., Radiation Effects, 1979, probabilities are W2 < 1% for % < 0.34 V.42, N.l/2, p.69-75. (effective porosity Peff = 9%) and W3< 5. Heinrich B., Gemende B., Luck H.B., 1% for* < 0.65 (Pcff. = 28%). Particle track membranes with higher porosity.- Proc.2-nd Meeting "Particle REFERENCES Track Membranes and Their 1. Fischer B.E., Spohr R. Production and Applications", Szczyrk, Poland, 1992, use of nuclear tracks: imprinting p.25-31. structure on solids, Reviews of 6. Albrecht D., Armbruster P.. Snohr R., Modern Physics", 1983, Vol.55, No.4, Roth M., Schaupert K., Stuhrmann p.907-948. H., Investigation of Heavy Ion 2. Flerov G.N., Synthesis of super-heavy Produced Defect Structures in elements and application of nuclear Insulators by Small Angle Scattering., physics method in neighboring regions. Applied Physics A, 1985, Vol.37, - Vestn.Akad.Nauk SSSR, 1984, No.4, p.37-46. p.35-48. pH-SENSITCVE MEMBRANES: TRANSPORT PROPERTIES IN AQUEOUS SOLUTIONS OF ELECTROLYTES

N.N.Kulov, A.N.Nechayev, N.I.Zhitariuk

The Kumakov Institute of General and Inorganic Chemistry , Moscow, Russia Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research Dubna, PO Box 79,101000 Moscow, Russia

Modified membranes with selective opposite direction (Fig. 2 - 4). The layer in the pores have been obtained on obtained results are due to the swelling of the basis of microfiltration poly(ethylene the grafted polymer containing in the terephthalate) track membranes by molecules tertiary nitrogen atom followed means of specially developed method of by its quaternization with HC1. The radiation-induced grafting (Fig. la, b). swelling leads to decreasing in the Rejection and flux of the obtained effective micropore size of the membrane membranes for aqueous solutions of selective layer. The obtained maximum electrolytes have been investigated. Their rejection level indicates there is no mosaic rejection (R) and flux (G) have proved to grafting in the pore of track membrane depend considerably on the pH value of and so all the pores have a thin selective the separated solution. Original PETP layer. After treatment of modified track membranes with pore size of 8 nm membrane with acid a considerable or lower change their properties in the amount of quaternized positive charged

Fig. 1 a. The cross-section of track membrane Fig. 1b. The cross-section of modified track membrane with selective layer in the pores KCL (0.01 M) 100 KCL (0.01 M)

t

10:

TT-mTTT0i RI I IRR RTP-M T N 11 y I R T i I R R I II I I R 11 \\ 4 6 610 0.0 2.0 4.0 6.0 8.0 pH pH

Fig. 2a. Rejection and flux as a function of pH values for track membrane

80 100

60

40: .1 40^ U Q0J2Q0 NoCI (1-1) CoCI2 (2-1) S0, (1 -2) •v \ QODOD Naa

R2-i Ri-i Ri-2 pH3 0 ^ 3' 4 r-'^r^ i 10 "3 10 "' 10 Ionic Force of Solution (M) pH Fig. 2b. Rejection as a function of pH values for modified Fig. 3. Rejection vs. ionic force of solutions of various type of track membrane with selective layer in the pores ions for track membrano

.0 0.5 1.0 1.5 2.0 2.5 0.5 1.0 1.5 2.0 2.5 Diffusion Coefficient, D»105 (cm!»s"') Diffusion Coefficient, D*105 (cm'«s"')

Fig. 4a. Rejection vs. diffusion coefficient of positive Fig. 4b, Rejection vs. diffusion coefficient of positive charged charged ions for track membrane Ions for modified track membrane with selective layer in the pores pH-scnsitive membranes: 61 groups appears in the selective layer (is ions from the membrane phase which is confirmed by electrokinetic flow potential positively charged. measurements). This fact, according to The influence of the mobility of ions the reverse osmosis separation theory, with the same charge on the selectivity of results in an increase of the membrane original and modified membrane with the rejection coefficient. selective layer has been studied. The The selective properties of the original experimental data show (Fig. 4) that, in and modified membranes in aqueous the case of modified membranes solutions of various electrolytes have also (positive charge), the rejection coefficient tor monovalent cations changes opposite been investigated (Fig. 3). The reduction + + of rejection coefficient depends on the to their mobility: (C2Hś)ąN Li Na ion valence type and the electrolytes are K Cs (the common anion is CV,pH 3). arranged as follows: R(2-i) R(l-l) The obtained correlation is explained by R(l-2). The obtained results are the electro-migrating transfer of ions qualitatively explained by proceeding through the pores, considered in the from the reverse osmosis charge frames of reverse osmosis charge mechanism through the Donnan mechanism. exclusion of co-ions and compensating

THE MEASUREMENTS OF KC1 AQUEOUS SOLUTIONS CONDUCTIVITY IN TRACK MEMBRANES PORES

V.V.Berezkin, OAKiseleva, V.D.Sobolev, N.V.Churaev, A.N.Nechaev

Institute of Crystallography of Russian Academy of Sciences, Moscow. Institute of Physical Chemistry of Russian Academy of Sciences, Moscow. Institute of General and Inorganic Chemistry of Russian Academy of Sciences, Moscow.

resistance measurement of membranes 1. INTRODUCTION set with membranes number changing Electrokinetic phenomena, arising in from 1 to 20. Further the electrical the case of liquid stream through porous resistance to membranes number media, contain information about relationship is plotted and extrapolated to solid-liquid interface state. But these infinite membranes number. The error, phenomena investigations are which has arised due to bad contact complicated in porous bodies due to between electrodes and membrane indefinability of their porous structure. surface, tends to zero in this case. Therefore using of track membranes is of The measurements were fulfilled at great interest in this investigations, cell, which scheme is shown in Fig. 1. because their pores are cylinders and The membrane set separates the cell resulting interpretation indefinability is into two electrically isolated parts A and minimized in this case [1]. Track B, and excessive electrolyte pressure may membranes are thin polymer films of be created in each of them. Electrolyte thickness 1 = 10 /im therefore solution exchange and membrane washing are electrical conductivity measurements are fulfilled under this pressure action. The very difficult inside their pores, essentially cell body was done of tetraftorethilene. in case of electrical double layers The cell temperature was regulated with overlapping. ultrathermostate and electrolyte Main electrical conductivity temperature was controlled with measurement error arises due to bad thermocouple, connected to digital contact between electrodes and voltmeter. The membrane set was fixed membrane surface [2]. This error is by two, covered with polyethylene, rings, comparable with value measured in case containing platinum electrodes with of small membrane thickness. The welded platinum nets. This construction measurement method, created by our minimized the gaps at group, allows to minimize this error. membrane-electrode interface and allowed to replicate the measurement 2. EXPERIMENTS results very well. This method concludes the electrical The measurement of electrical R-1CT, Ohm

3 n-16

2 N-S o-o-o -G- 1 •

0.5 NFWT

Fig. 1, Schematic representation of the apparatus Fig. 2. Determination of the electrical resistance R, of the solution (o = 10-4 M, KCL) in the membrane pores (D = 40 nm) at 24 °C. Here: f — frequency, Hz; n — the number of mombranes conductivity was performed with membrane number in set was being alternative current bridge. It is known, changed from 1 to 16. that measurement errors, followed from The porosity IT of porous media, polarization phenomena at electrodes, containing electrolyte, is equal to [4]: are neglegible at high frequency and do not influence solution resistance n = £ -fi' (1) measurement accuracy [3,4]. Preliminarily the mebrane resistance measurements Where E - reduction coefficient of were fulfilled in frequency band from electrical conductivity; P - tortuosity. 1000 Hz to 200 kHz. The resistance - 1/f For track membranes = 1. In this value (f-alternative current frequency) case: relationships for two sets with different numbers of membranes with pore diameter of 40 nm are shown in Fig. 2. n = (2) The extrapolation of this relationships to Ko infinite frequency allow to except the where K - electrical conductivity of influence of regions near electrodes to membrane, containing electrolyte measurement results and to define the solution; ohmic resistance of membrane, containing solution. It is seen from Fig.2, Ko - electrical conductivity of bulk that the resistance, measured at frequency solution. of 200 kHz, and resistance at infinite The measured cell resistance R is the frequency are practically the same. So sum of membranes set resistance and further membrane resistance resistance Ro, arising due to the bad measurements were performed at contact between electrodes and frequency of 200 kHz. membrane surface. R = nRm + Ro (3) There is the probability of pores where Rm - the resistance of single overlapping in the membranes set. But membrane; the membranes were clutched in cell n - the number of membranes in the set. slightly and we supposed, that there was no overlapping if only the membrane 1 number in set was less than 18-20. To Rm = Kons (4) determine the membrane porosity the cell was filled with KCL aqueous solution of L 10-1M concentration. We supposed, that Ro = (5) the contribution of KoS was neglegible under this condition. The The measurements of.. 65

l/n where I - membrane thickness; S - membrane area; zoo L - thickness of a gap between electrodes and membranes. In result of easy transformation are con obtain the following relationship:

150 - 1 = 1L , 1 TT n 1 + no (6) where II - the measured membrane porosity; 100 no- the real membrane porosity. The l/Tl(l/n) relationship is linear, and 1/TIo value | may be determined as length of 1/TT axis, cutted by this relationship at 8/ n. The relationship l/Tl(l/n) for 50 membranes with pore diameter of 40 nm is shown in Fig. 3. The measurement

i5 R results were treated with least square ' — 4r" - - WW"5 fl.-0.059 IS TM nEMIMNI method. Membrane porosity IIo, determined this plot, is equal to 0.039, what remains in a good agreement with D.5 value of 0.0363, determined with the 1.0 1/1 electron microscopy method, and value of Fig. 3. Determination of the porosity, j], using various number of the membranes, n 0.0393, determined by the rare gas filtration method. Hence the supposition of pores overlapping absence, made above, istrue. So the simple, accurate, and convenient conductivity method maybe suggested for membranes porosity measurement.

3. RESULTS If membrane porosity is known, the 30 electrolyte effective specific conductivity inside pore K may be calculated and compared with specific conductivity of bulk solution Ko. The KCL aqueous solutions 20 conductivity in track membranes pores of diameters equal to 40 nm, 105 nm, 190 nm and 265 nm has been investigated. The relationships between a = K/Ko value and 10 solution concentration for membranes with pore diameters mentioned above, are shown in Fig. 4. The fast increase of electrical conductivity as solution concentration and pore diameter are -1- —r~ —i—• 1— diminished is explained by the J to" I0 to-« to- considerable contribution of double electrical layers diffuse parts to electrical Fig. 4. Dependence of the coefficienta a = KJKo on the conductivity (surface conductivity concentration of KCL solution C, and the diameter of membranes pores, D. Here; 1 — D = 40 nm; 2 — D = 105 phenomenon). nm;3 — D = 190 nm;4 — D = 265 nm. We hope that results obtained will be 2. Electrokinethical properties of capillar helpful in track membranes properties systems. Proceedings under I.I.Zhukov investigations. guidance. Moscow-Leningrad. AS USSR Publishing, 1956, 352 p. REFERENCES 3. R.de Levis., Electrochim. Acta, 1956, 1. G.N.Flerov., Superheavy element N 10, p.395. synthesis and nuclear physics methods 4. Lopatin B.A., Electrochemical method application in neighbouring fields. of analysis. Theoretical basis. Moscow, Vestnik of USSR Academy of Science, High School, 1975, 265 p. 1984, N4, p.35-48. TRACKS OF HIGH-ENERGY IONS IN POLYIMIDE: I. PROPERTIES OF POLYIMIDE IRRADIATED BY HIGH-ENERGY IONS

AJ.Vilensky, V.A.OIeinikov, Yu.V.ToImachyova, N.G.Markov, E.P.Dontzova

Institute of Crystallography Russian Academy of Sciences Moscow, 117333, Leninsky pr.,59

Abstract. Properties of polyimide irradiated by high-energy ions of Ar (the energy 40 MeV) and Kr (the energy 210 MeV) were investigated. It was found that as a result of high energy ions irradiation destruction of imide rings with formation of amide groups and intcrmolecular bonds takes place. The dichroism of bands in polyimide spectra and also dependence of chemical resistance on surface density of polymer irradiation were studied.

The influence of ions beams with 1. INTRODUCTION significantly less energy (0.05-0.2 MeV) Nowadays nuclear filters (track on the PM was studied [3-6]. membranes (TM)) are perspective Investigations concerning the influence materials for membrane technique. These of varions types of irradiations on PM structures are made by means of the were performed for: irradiation of initial material by • TJV irradiation (the wave length 185 high-energy ions beam and following nm)[7,8]; development of formed latent tracks in • irradiation (more than 2000 Mrad) this material [1,2]. [7,9]; Track membranes made on the base of • ions beams H , He , Kr , Xe , with polyethyleneterephthalate and energies from 0.5 to 2 MeV [3-6]; polycarbonate are manufactured in a as well as low temperature plasma number of countries. But applications of discharges of various types. these membranes have some limitations The typical results of these irradiations which are defined by physico-chemical are: properties of TM materials. Therefore • The destruction of imide cycles takes intensive research in the field of TM dace. It was noted in some papers creation on the base of another materials 6,11] that the number of aromatic have been performed. For this purpose fcycles does not change. polyimide (PI) is the most perspective • The gases eduction (O2, N2, CO) polymer because of its great thermal and appears[7,12]. radiation resistivity. • The increase of adhesion activity of Important step in the way of polyimide surface and their hydrofilization is TM creation is the investigation of the observed. interaction of high-energy charged • There is an increasing of particles with this polymer and the change electroconductivity, probably of PM structure as a result of action of connected with polymer grafitization high-energy ions with energies enough for [3,4,8]. the formation of pores in PM films (the In present work the investigations of energy more than 1 MeV/nucleon). influence of high-energy ions (die energy J2.1/T--10, expx 20). The optical density 1-2 MeV/nucIeon) on the PM were was calculated as an average of the least performed. The alterations of polymer three measurements for each sample. The structure as a result of ions irradiation errors connected with thickness variations (imidization and macromolecules of PM films were excepted by averaging orientation) as well as changes of of optical densities for 7-10 samples. chemical resistance and To investigate possible changes in physical-mechanical properties of olymer macromolecules orientation after ions-irradiated PI were studied. PI films irradiation, the method of dichroism ratio measurements was used. 2. EXPERIMENTAL The absorption of polarized IR-racliation PI films were prepared by means of in dependence on the PI films deposition of the polyamide acid orientations was measured. Samples were (PAA)solution on the forming surface. oriented both normally and with tilt 45o PAA was synthesized on the base of with respect to incidence ray [J4,15]. pyromellitol dianhydrite (PMDA) and The estimatii)/! of chemical resistance 4,4-diaminodiphenyI ester (DADFE) in of ions-irradiated PI films was carried out dimethyl formamide (DMFA) with the by measuring of PI etching rate in 5% following thermoimidization. The residual NaOH solution at 90f1C. The etching rate solvent content was estimated as the was determined by sample weight change weight loss of sample as a result of the with the accuracy of 0.1 mg. thermotreatment of samples at 400°C, for The results were processed by 40 min, with the use of the firm "Dupont" mathematical statistics methods, where device. confidence coefficient was 0.95 [16], PI films in thickness of 10±1 and 20+1 /um were studied. The residual solvent 3. RESULTS AND DISCUSSION content (DMFA) was 1.1% and 1.3%, Dependencies of intensity of typical PI respectively. After thermotreatment at absorption bands on track density in the 320°C, for 2 hours, the content of DMFA sarnples were studied. Decreasing of 1380 was decreased to 0.6%. Thus, these foils cm", 1720 cm'1, 1776 crrr bands and the foils "Kapton" ("Du Pont") or (oscillation of groups contained in imide "Upilex" (Ube Industries Co. Ltd.) are rings), 1244 cm"1, 1180 cm"1 1290 cm"1 similar. bands (ester groups oscillations), 1020 Physico-mechanical properties of both cm, 1512 cm bands (benzene rings initial and irradiated by Kr ions PI films oscillations), 726 cm, 885 crn ones (the longitudinal strength and breaking (amorphous sensitive bands) [7] was elongation) were measured. observed. The dependencies were PI films were irradiated by Ar ions with nonlinear: the more tracks density (10 ), the energy 40 MeV (IMeV/nucleon), the more decreasing of absorption bands. using cyclotron in A.F. Ioffe The dependencies of optical density Physics-Technical Institute (St.Peterburg, D726 of /26 cm" band (deformation Russia), and by Kr ions with the energy oscillations of C=0 bonds of imide rings) 210 MeV (2,6 MeV/nucleon) in the on surface density of ions irradiation cyclotron U-400, G.N.Flerov Laboratory (both for thermotreated PI and without of Nuclear Reactions of Joint Institute of one) are presented in Fig. 1. It is known Nuclear Research (Dubna, Russia). [7], that the treatment of PI films at the The irradiation density was controlled high temperature gives the partial by the count of holes number in the destroy of imide rings with formation of samples after their treatment in acidify intermolecular bonds, therefore D726 is KMn04 solution at 80°C, during 5 hours decreased for thermotreated polymers in [13]. comparing with the non-thermotreated The IR spectra were recorded using one. The decrease of D726 for spectrophotometer Specord M80 with ions-irradiated PI points that the cycle measurements program with the destruction of imide rings is takes place in same wave number (0.21 start, slit this case. It should be noted that for Tracks of high-energy 69

's i

Fig. 1. Tho dcpondonclos of D7;o optical absorption rionsity (deformation oscillations cf C-0 bonds of Imldo ringo) as n function of surfaoo density of PI Irradiation by Ar Ions: 1 — termotreated film; 2 — non-termotreated film thermotreated PI (Fig. 1, curve 2)D726 Fig. 2. Tho dopondonolea of PI film etching rate in 5% NaOH solution (90°) as a function of surface density Irradiation by practically does not depend on irradiation Ar Ions: 1 — termotreatod film; 2 — non-tormotreated film density up to 10-10lucm . This phenomenon is connected with high radiation resistivity of PI. of polymer due to their exposition to Appearance of 1680 cm and 1550 high-energy ions beam were carried out by cm" absorption bands (amide, groups measuring of dichroism of 726 cnii , 1380 oscillations) and 1680 cm ones cm , 1512 cm' and 1776 cm bands for (mtermolecular bonds) confirms the films oriented both normally to the imide groups destruction in PI exposed by incident IR-ray and with the tilt 45°. The Ar Jons with density of irradiation 10 - results are shown in Table 1. 10 cm" . It may be explained by the The films normally oriented to the amide groups formation (1680 cm - falling IR-ray are practically isotropic. It is Amide-f and 1550 cm'1- Amide-2) [7,14], true for both inital and irradiated by Kr and also by the crosslinkage bonds ions films. In the case of film oriented with creation (1660 cm" ) [7]. the tilt 45° the dichroism ratio increases Besides, both 726 cm'1 and 885 cm"1 with increasing surface density of ions bands are amorphous sensitive [171. irradiation. This fact points out to the Therefore the decreasing of D726(Fig.l) additional orientation of polymer and D885, as well simbath increasing of macromolecules along the track axis. crystal sensitive band Dsoo tells about the The mechanism of this orientation is structural changes in polymer. It is likely, not clear now. It can be connected with these changes are caused by regulating of processes, which take place in polymer polymer chains as the result of imide rings due to tracks formation. destruction and crosslinkage bond In Fig. 2 curves of relative etching rates formation [7,9,17], of PI films in 5% NaOH solution at 90°C The decrease of bands intensities in the as a function of Ar ions irradiation density range 900-1500 cm points out the are shown. The etching rate of destructions of multiester groups and thermo-treated polymer is less than the simple ester bonds with removing etching rate of the initial one. Probably, it aromatic molecules fragments as a result is caused by the additional intermolecular of the ions irradiation. The same changes linkage formation in thermal treatment are observed in PI films after their process. thermotreatment at temperatures above At increasing the surface density of ions 400°C [18]. irradiation the number of intermolecular Investigations of additional orientation linkages increases. It is defined by the Table 1. Dlchrolsm of PI absorption spectra (PI films thickness Is 20,um, non-thermotroated, PI was Irradlatod by Kr Ions) R — films woro normally oriontod to fallen IR-ray; R* — angle between normal and IR-ray direotlon Is 45°

R/R* Wave Surface density of irradiation, cm"2 number cm'1 0 107 108 109 726 1.00/0.91 1.09/0.95 1.04/1.17 1.06/1.17 1380 0.94/0.96 0.94/1.20 0.97/1.20 0.97/1.25 1512 0.91/0.90 1.01/1.47 1.07/1.35 1.05/1.50 1776 1.05/1.05 1.02/0.97 1.11/1.16 1.10/1.20 rising of PI chemical resistivity. But for and intermolecular linkages formation in the fiuence higher than 10 cm" , the part ions action zone take place. The of destructing polymer in cores of ions dichroism ratio changes in the samples tracks is increased. Thus, there is a oriented with the tilt to incident IR ray minimum on the curve of the function of was also observed. etching rate versus fiuence. The rise of these ratio points out that However, the decrease of PI etching additional macromolecules orientation rate for low fiuence cannot be explained have occurred in the process of tracks on the base of intermolecular bonds formation. Decrease of etching rate of PI created in the zone of ions passing only. It is observed fifor surface density of is true, if we use the size of changing irradiation 10-10 ions/cm . It can be structure zone for PETP estimated by explained by "long distance effect". means of conductometry [19] or layer by Surface density of ions irradiation in the layer etching method [20]. The size of this range up to 10 cm" practically has no zone is 50-70 nm. Thus, the part of sewed influence on physical and mechanical volume (volume with higher density of characteristics of PI. intermolecular bonds) is 10" % when Acknowledgement fiuence is 10 cm". Therefore, it should be supposed that the ion acting zone is We are very thankful to Prof. significantly extended. The same "long Yu.Ts.Oganessian for his permanent distance effect" when a ion passes through interest to this work, discussion of the the substance was theoretically found in results and support in carrying out the the work [21] and was experimentally experiments. We are also grateful to discovered, by means of investigation of A.Yu.Didyk for irradiating of PI film by DMFA absorption the irradiated Xe ions high-energy ions by means of the PETP [22]. cyclotron U-400. The results of investigations of the REFERENCES high-energy ions influence on the physical and mechanical characteristics of PI show 1. Flerov G.N., Vestnik AN USSR, 1984, that the Eradiation of film by Kr ions in No.4, p.35-48. range 10-10 ions/cm practically has no 2. Fisher B.E., Spohr R., Reviews of influence on both breaking elongation Modern Physics.,1983, Vol.55, No.4, and longitudinal strength. pp.907-948. 3. Davenas J.,Boiteux G., Xu X.L., Adem 4. CONCLUSION E., Nuclear Instrum.& Meth. As a result of PI films irradiation by Phys. Research, B, 1988, Vol.32, ions with energy 1-2 MeV/nucleon the No.1-4, pp.136-141. imide rings destruction with amide groups Tracks of high-energy., 71

4. Fink D., Muller M., Chaddertion L.T., 13.Komaki Yo., Matsumoto Ya., Channington P.H., Elliman R.G., Ishikawa N., Sakurai Ts., Polymer McDonald D.G, Nuclear Instrum. & Communications, 1989, No.2, Meth.Phys. Research. B,1988, Vol.32, pp.43-44. No.1-4, p.125-130. 14. Elliot A. Intrakrasnye spektry i 5. Koul S.L., Campbell I.D., McDonald struktura polimerov., Mir, 1972, p.160. D.C., Chadderton L.T., Fink D., 15.Laius L.A., Vysokomolekulyarnye Muller M., Nuclear Instrum.A soed., A, v.16, No.9, pp.2101-2106. Meth.Phys. Research, B, 1988, Vol.32, 16.Charykov A.K. Matematicheskaya No.1-4, p.186-193. obrabotka resultatov chimicheskogo 6. Vandcrline W.F., Ruoff A.L., analiza., "Chimiya", 1984, p.162. J.Vac.Sci. & Technol., B, 1988, Vol.6, 17.Pshenistsina V.P., Kazaiyan L.G., No.6, p.1621-1625. Lurye E.G., Lebedinskaya M.Ya., 7. Bessonov M.I., Polyimidy - novyj klass Kovriga V.V., Vysokomolekulyarnye termostojkih polymerov., "Nauka", soed., A, 1972,V. 14, No.3, p.628. 1983, p.307. 18.Adrova N.A., Artyuhov A.I., 8. George M.A., Ramakrishna B.L., Baklagina Y'u.G., Borisova T.I., Koton Glaunsinger W.S., J.Phys.Chem., 1990, M.M., Mihailov N.V., Nikitina V.N., Vol.94, No.12, pp.5159-5164. Sidorovich A.V., 9. Bartenyev G.M., Karimov S.N., Vysokomolekulyarnye soed., A, 1973, Narzullaev B.N., Kabilov Z.A., V.15, No.l, p.153. Matveev V.K., Sarmina V.I., 19. Apel P.Yu., Chimiya Vys. Energii, Vysokomolekulyarnye soed., A, 1977, 1991, V.25, No.2, p.132. V.19, No.10, pp.2217-2223. 20.Vilensky A.I.,01einikov V.A., 10. Friedrich J., Loescheke I., Mchedlishvili B.V., Chimiya Vys. Intern.Journ.Polymer Mater., 1990, Energii, 1992, v.26, No.4, pp.300-304. Vol.13, No.1-4, pp.39-51. 21.Goldansky V.I., Lantsburg E.Ya., 11. Obuhovskaya O.F., Stefanovich N.N., Yampolsky P.A, Pisma v JETF, 1975, Vladykina T.N. In "Novye klei i V.21, No.6, p.365. tehnologiya skleivaniya", Mosk. Dom 22. Smclyansky A.S., Zhdanov G.S., Nauchno-Tehn. Propagandy im.F.E. Klinshpont E.R., Milinchuk V.K., Dzerzhinskogo, 1976, pp. 71-77. Chimiya Vys. Energii, 1993, V.27, 12. Korchak V.V., Lyashevich V.V., Rode No.3, pp.19-23. B.B., Bygodskii Ya.S., Vysokomolekulyarnye Soed., A, 1980, V.22, pp.71-77.

TRACKS OF HIGH-ENERGY IONS IN POLYIMIDE: II. ETCHING OF TRACKS. PRODUCTION OF POLYIMIDE TRACK MEMBRANES

A.I.Vilensky, E.RNickolsky, VA.Oleinikov, D.L.Zagorsky, B.V.Mchedlishvili, N.G.Markov, E.P.Dontzova

Institute of Crystallography, Russian Academy of Sciences Moscow, 117333, Leninsky Pr.,59

Abstract. The processes of high-energy ions tracks etching in polyimide (PI) were studied. Comparison between characteristics of etchants with various compositions was made. A new etchant (concentrated hydrogen peroxide) with high selectivity and high enough etching rate was suggested. The etchant is accessible and ecologically clean. PI track membranes for ultra and microfiltration were created.

the PI solvents, such as solutions based on 1. INTRODUCTION hydrasinhydrate and ethylendiamine At present one of the most widely used [9,10], base solutions of ethanol or technological proccesses of separating of propanol [11]. complex mixtures is the membrane In the present work the known filtration [1]. Among those materials, methods of tracks etching in PI were which are used in this process, track evaluated and compared (the PI films membranes (TM) fill a highly important used were identical, irradiated under the place. TM are made by polymer film same conditions). The information about irradiation by a beam of high-energy ions design and investigation of new methods with the further development of the tracks of TM producing from PI is, provided. up to the through pores formation [2-4]. Polyimide is promising as a material for 2. EXPERIMENTAL PROCEDURE manufacturing of chemical, thermal- and As the subject of investigation we used radiation-damage stable membranes. The the manufactured PI film of 10 and 20 fim composition for the tracks etching in PI thickness. To investigate the influence of (KMn04 in H2O2) was first suggested in residual solvent content on the etching the work [5]. In [6,7] conic or cylindrical process of the irradiated polymer, a part pores in this polymer were obtained by of the film was thermotreated at 320°C etching of irradiated PI of specification during two hours, with the residual solvent "Upilex" of the Ube Industries Co. Ltd., content (RSC) reduced up to 0.6%, what with thickness of 25 in 25% KMn04 corresponds to the RSC in PI film of solution at 90°C with the following "Kapton" or "Upilex" marks. washing off manganese oxides by chloride The PI film was irradiated by ions of acid. argon, krypton, wolfram and by fragments For reagent KMnCM mixed with HCIO3 of uranium fission: or KMn04 mixed with H2O2 was also - the Ar ions irradiation (energy 1 suggested [6,7]. Saturated solution of MeV/nucleon) was conducted in the K2CT2O7 in 12N, 16N, 24N H2SO4 as well cyclotron in Ioffe Physics-Technical as 4.5N NaOH were also used for PI [8]. Institute (St. Petersburg); the film of 10 For the tracks etching one can also use fim in thickness was used; - the irradiation by Kr-ions (energy 0.3 electron microscope BS 340, TESLA, was MeV/nucleon) - in the cyclotron U-400 used. (Flerov Laboratory Nuclear Reactions, Dubna), film of 20.um in thickness; 3. RESULTS AND DISCUSSION - the irradiation by W-ions (energy 0.3 The results of tracks etching in PI MeV /nucleon) - in the accelerator in the investigations by solutions of different Institute of Theoretical and Experimental compositions are tabulated in Table 1. Physics (Moscow); The results given in [6,7] are not reproduced. In PI films irradiated by - the irradiation by fragments of Ar-ions and treated by 25% [7] and 19% uranium fission - in the Karpov solutions KMn04 in H2O (Table 1, p. 1-2), Physicochemical Science Research there are not etched tracks though this Institute (Obninsk). solution destroys PI surface quickly The essential difference of the latter enough (let us note that the KMnO.i kind of irradiation from the irradiation in solution in H2O at 100°C accounts for accelerators is wide range of ions tracks 19%). These results were not explained directions, what is a result of a relative though the film types used in the research close position of PI film and the fission were alike to ones used in [6,7] and Cu fragments source. Let us note that for and S-ions by their weight and energy irradiation by means of accelerators the were alike to Ar ions. Because of this, ion tracks are practically perpendicular to they carried out investigation of influence the PI film surface. pH value of KMnO solution on selectivity The energies of Ar and Kr ions were of tracks etching in PI. At pH > 7 the high enough to make through tracks. The selective etching of tracks does not range of W ions tracks account for 10 jum happen. If the solution is acidified the of length. This is enough to obtain etching becomes selective; the etching deadended tracks in initial films of 20 fim selectivity (that is the ratio of rate of in thickness. The surface density of etching along track to radial etching rate) irradiation was varied between 10 and exceeds 10 . Let us note that in such 10 ions/cm . This range of values for conditions the oxidant potential of Mn04- tracks density allowed to produce ions is at its maximum. membranes as for microspores diameters In the oxidant mixtures, offered in [7] 0.05-2.5 yum) so also for ultrafiltration (Table 1, p.4-6), the pores etching rate is (pores diameters below 0.05 fim). The superior to acidified solutions of KMn04, etching of irradiated films was carried out but the selectivity is much worse. at the temperature of 20-100°C. The tracks etching in chrome mixtures The film thickness during the (Table 1, p.7) passes quick enough (3-6 treatment has changed, approximately of min). However, the etching selectivity is 1 fim. The pores diameters were defined not high, the intensive surface etching is by a hydrodynamic method by the well seen. distillated water flow through a As for base etchants (5% KOH in membrane at a given differential water, hydrasinhydrate and etylendiamide pressure (square of membrane amounted solutions) in some cases there are a to 0.55x10" m , differential pressure - through pores formation, but the etching 510 Pa) [1], and also by the scanning selectivity is not sufficient. For each electron microscopy of surface and break studied mixture the etching rate of of membranes. The etching rate of thermotreated films was a little bit lower non-irradiated films was defined by a than the one of non-thermotreated films. method of weight and by the film Analyzing the results we can conclude thickness change determination by that the examined compositions do not electron microscopy. To obtain breaks, suit well for practical use in technological membranes were cooled to the liquid process of TM manufacturing on PI basis. nitrogen temperature, the conducting Basic etchants are not selective enough. layer was deposited by Au or Cu The etchants on the basis of oxidants give evaporating in vacuum. The scanning pore structure, but they are highly Tracks of ... 75

Table 1. Etching of polyimide by solutions of different composition. Films thickness is 10 /

2. 19% sol. KMn04 100 8 9.9 absence of pores 100 12 6.8 absence of pores 3. 25% sol. KMnC>4 90 4.5 0.1 acidified by H2SO4 90 S.5 0.2 ~2T%H202+^%l^n04 100 15 2-3 0.4-0.6* 100 15 2-3 0.5 5. 50%H2Oz+50%KMnO4 100 15 5 0.33-0.35 100 15 9 0.5 6. 75%H202+25%KMn04 100 15 9 0.2* 100 15 9 0.3

7. 24N H2S04+K2Cr207 90 0.08 4 0.15 8. 5% solutionKOH 90 0.0s 6.6 0.1 9. 0.1N sol. KOH in 60 15 13 absence of pores* 10. 5% sol. KOH in 70 0.16 4 absence of pores ethanol 11. 5% sol. KOH in 80 0.16 8 0.08 10% ethanol 12. 5% sol. KOH in 70 0.05 3 0.08 501% ethanol 13. 25% p-p 70 0.05 6 0.1 hydrasinhydrate * PI films were thermotreated (at 320°C, for 2 hours).

Fig. ia. Micropnotograph of surface of Pi track memoranes. Fig.ib. MICROPNOTOGRAPN of surface or Pi TRACK membranes. PI film WAS Irradiated by Kr-ions Irradiation by fragments of uranium fission Table 2, Etching of polyimide by hydrogen peroxide at 90°C Etching Average Irradiation time, diameter hours of pores, fim Ions Ar, 5x10'cm"" 5 0.15 Energy of 1 MeV/nucleon, non-thermotreated 10 0.35

Ions Kr, lxlO7 cm"2 5 0.25 Energy of 2.h MeWmideon, non-thermotreated 10 0.45

Ions W,4xl07cm"2 Energy of 0.3 MeV/nucleon, 5 0.85 non-thermotreated

Ions Ar, 5X107 cm-2 5 0.15 Energy of 1 MeV/nucleon, thermotreated 10 0.35 corrosive, toxic, and need a long washing discrepancy shows that for small to remove products of etching. Besides diameters of pores the radial etching rate wastes of the process are ecologically depends essentially on the tracks dangerous. structure. We consider the PI treatment by 30% Figure 1 shows the SEM pictures of solution of hydrogen peroxide is more characteristic surfaces of PI films which perspective etching process [2]. PI were etched in 30% solution of H2O2 at treatment with the suggested etchant goes 90°C during 10 hours. In comparison to quickly and does not need careful surfaces of TM etched in others reagents, washing. The process of pores etching in the surfaces of these membranes are this way is charactized by high selectivity. smooth, pores outlines are sharply The results of investigation of PI identified. The angles of ions directions treatment in H2O2 are tabulated in Table are well seen. 2. (The etching results of inital and heat Figure 2 illustrates replicas of TM treated PI films of 10 and 2Q«m in surfaces of PI and PETP (irradiation by thickness, irradiated by Ar, Kr and W Ar-ions). Surfaces of TM pores of PI are ions). significantly smoother than surfaces of The tracks etching rate in PI increases TM pores of PETP, which have many with the loss of specific energy of ions defects. mount. So, for Ar, Kr and W average value of radial rate of etching (in 30% 4. CONCLUSION H2O2 solution at 90°C) is egual to 15, 23 Different ways of etching of TM on PI and 60 nm/h, respectively. For these base were studied. It was established that pores, which diameters are below 0.4 ^m, the etchants given in literature are not the radial etching rate values practically enough suitable for pore structure do not depend on the thermal treatment formation in this polymer. A new etchant of a film, while the etching rates of suggested in this work (hydrogen peroxide non-irradiated films amount in the same solution of 30% concentration) possesses conditions - for initial - to 60 nm/h, for high selectvity and proper etching rate thermotreated - to 30 nm/h. This comparable with the other ones. After hydrogen peroxide treatment filtres do Tracks of.. 77 not need long washing for etching 5.Fleisher R.L., Price P.B., Walker products removal. The etchant is R.M., Nuclear Tracks in Solids. accessible and is less toxic in comparison Principles and Applications. Berkeley, with other etchants. It is possible to use 1975. this etchant in the technological process 6. Komaki Y., Matsumoto Y., Ishikama of PI track membranes manufacturing. N., Sakurai T., Polymer Commun., Using above results, filters for ultra- 1989,30,pp.43-44. diameters of pores below 0.05 fim) and 7. Ishikawa N. et.al., Japan Patent No. microfiltration (diameters of pores X2-47141. 0.05-2.0 fim) are being realized. 8. Samoilova L.I., Apel P.U., Kuznetsov V.I., Tretyakova S.P., Solid state track REFERENCES detectors of nucleus and their usage. 1. Brock T., Membrane nitration. A Dubna, 1990, pp.33-36 Publ.of Science Tech., Inc. Madison, 9.Atsachi E.. J.Electrochem. Soc.,1985, WL, 1983. 132, No.l, pp.155-158. 2. Flerov G.N., Vestnik of USSR S.A., 10. Patent Japan No.N61-83235. 1984, No.4, pp.35-48. 11. Patent USA No.4426253. 3. Fisher B.E., Spohr R., Reviews of 12. Method of polyimide track Modern Physics., 1983, Vol.55, No.4, membranes making, Patent pending pp.907-948. N 92-003092. Accepted 11.06.93. 4. Accelerating capillary membranes and their use in national economy. - Materials of intern, congress. Poland, 1990. Apel P.U. and others, pp.71-73, Tretyakova S.P., Schirkova V.V., pp.53-61.

TRACKS OF HIGH-ENERGY IONS IN POLYIMIDE: III. INVESTIGATION OF ETCHING PROCESS, TRACKS STRUCTURE AND PORES FORMS IN THE TRACK MEMBRANES OF POLYIMIDE

A.I. Vilensky, E.E. Nickolsky, V.A. OJeinikov, D.L. Zagorski, B.V. Mchedlishvili, N.G. Markov, E.P. Dontzova

Institute of Crystallography, Russian Academy of Sciences Moscow, 117333, Leninsky Pr., 59

Abstract. The results of investigations of pores formation process in polyimide films after their irradiation by argon, krypton and wolfram high energy ions with the further treatment in concentrated hydrogen peroxide are presented. The size of the destruction zone and the zone of formation of a changed polymer structure as well as chemical resistance increasing are defined. The rate of etching of polymer along tracks and etching selectivity are determinated. A method of preparing the polyimide track memhranes with cylindrical or conic forms of pores is shown.

[8,9] there is only information about the 1. INTRODUCTION form of pores, obtained by Cu and S ions A method of track membranes making track development in PI film. It has been is universal and may be applied for many established by the authors of [11] that the polymers, including polyimides, with very concentrated solution of hydrogen good radiation resistance and peroxide (30% solution of H2O2) is the thermostability [1]. Size and forms of perspective reagent for track etching in membranes pores are being determined 'I. both by the high-energy ions track The object of present work, is to structure and by the means of their investigate the processes of PI etching in development (etching). The characteristic this reagent, and tracks structures as well radius of a track depends on ion charge, as pores forms and sizes. energy and a little bit less on polymer composition [2]. And vice versa, a 2. EXPERIMENTAL PROCEDURE polymer composition defines the process As a research object we used PI films of pores formation and development with thickness of 10 and 20 fim as initial from latent tracks, the choice of etchants ones (with the residual solution content and treatment conditions. Only for (RSC) of 1.1%) and PI films after polyethyleneterephtalate (PETP) the thermotreatment (temperature 320 C, etching mechanism has been studied well 2hours, RSC 0.6%) [10]. enough by now [3-5]. The processes of The PI film was exposed to radiation polypropylene and polycarbonate etching by ions of argon (1 MeV/nucleon), [6,71 were also investigated. krypton (2.6 MeV/nucleon), and wolfram Some compositions of polyimide (PI) (0.3 MeV/nucleon) [10]. etching solutions are suggested in The membranes pores structure [1,2,8,9]. The solutions contain strong investigation was conducted on the oxidizers such as KMn04, K2Cr207. scanning electron microscope (SEM"! Pores formation mechanism for this BS-340, TESLA. Conducting layers on polymer was not studied yet. So, in works the membranes surface (20-40 nm in thickness) were formed by Au or Cu evaporating in vacuum. To investigate the pores structure the polymer was broken at -<::0->o-°-o the temperature of liquid nitrogen. The density of track membranes pores was H 0 between 1Q7—108cm~2. The pores 2 2 diameters were determined by a hydrodynamics procedure. The etching rate along track Vt was determined from the time it took for a through pore formation, the radial rate - from the curve of etching time dependence of pores radius r(t). The etching rate of The imide rings are destroyed when act non-irradiated polymer was measured by upon by hydrogen peroxide. The forming a weight method and by a thickness amidoacid is being removed from the change defined by means of SEM. polymer. IR-spectroscopic investigations were Fig.l shows the Di776 change related carried out on a spectrophotometer to time of etchingt of PI in H2O2 for Specord M80, in the range of wave different conditions of irradiation. These dependencies, as well as those of D726(t), number range between 1800 and 700 which behave in the same manner, are cm" . The surface density of hish-enerev correlated with the total area of ioncL irradiation (fiuence) was membranes surface and, therefore, they cm" . are defined by the polymer decrease in 3. RESULTS AND DISCUSSION quantity as it dissolves. Previously [10] it was established that The most intensive decrease of as a result of PI exposure to hijrh energy Di66o(r) is characteristic of the D166O ion radiation the imide rinrs destruction relation to radii of etched pores r (Fig.2) with amide groups formation ta'•<;.; place. at pores radii below 5-15 nm [10]. Further This was well-seen on IR-spectra, where the value of optical density of this band the optical density of absorption hands changes much slowly. Thus the Di776 and D726 decreased (1776 cm" and intermolecular bonds are formed in 725 cm" are the bands of deformable and cylinder around track spaces of 5-15 rim valence oscillations of C=0 groups of imide rings) and new absorption bands have appeared. Those bands were typical Fig. 1. The relation of optical density of the absorption band for amides 1680 cm (Amide-1) and 1550 1776 cm"1 to time of polyimide film etching (thickness of 10 fim, RSC 0.6%); 1 — initial fiim; 2 — irradiation by Ar-ions, cm" (Armde-2) and intermolecular bond density-10 ions/cm2; 3 — irradiation by Kr-ions, density-10 1 160 cm" [10,12,13]. ions/cm2; 4 — irradiation by Ar-lons, density-10 ions/cmz On PI film treated by hydrogen peroxide the intensity of these bands were the same. This reagent action on the irradiated PI films causes appearing of 1680 cm and 1550 cm absorption bands, appearing and decreasing of the magnitude of the Di776 and D726 bands. The process of imide rings destruction by hydrogen peroxide is most likely to be proceeded by a alkali hydrolysis mechanism. Such a process can be described schematically like: I 0 ! 4 i 8 10 t.h Tracks of high-energy ions in...

Fig. 2. The relation of optical density value of band 1660 cm-1 which characterizes the number of intermolecular linkages, to radius of etched pores radius. This is directly confirmed by the kinetics of change of pores radii which were formed as the PI film of 20 fim in Fig. 3. Kinetics of PI film (thickness of 20 ftm, thickness, irradiated with surface density non-thermotreated, irradiated by Kr-lons with energy of 2.6 of 10 cm by Kr-ions, was being etched. MeV/nucleor. and surface density of 109 cm"!) etching in The four characteristic stages of etching hydrogen peroxide at 90°C. A — the film was transferred from the etching solution into a cell for pores radii process are well seen. determination by means of a hydrodynamlc method without At the first one (duration of such drying; o — after every step of etching polymer was dried conditions approximately 10 min) there is a quick pores etching up to the radius of 5 nm, the polymer etching rate along track after polymer drying. Considering that constitutes Vx- 1000 nm/min, the radial the pores diameters practically do not etching rate is Vr- 0.5 nm/min and depend on the treatment mode, we can corresponds to etching rate of say that the influence of polymer swelling non-irradiated PI polymer after the was small. This was also confirmed by the thermotreatment Vh- 0.5 n^n/min [11]. So, absence of the absorption bands of water the etching selectivity in this state is V = in PI films which were etched and then Vt/Vr = 2000. dried on air. By this means, a cylindrical At the second state (10-60 min) there zone around a track of a high-energy ion is an essential slowing-down of etching with PI resistance increased is formed, process. We suppose this is connected that may be connected to the with the polymer resistance increase due intermolecular linkages formation [12,13]. to formation of a zone with density The biggest chemical resistance abnormally high or due to another corresponds to the radius of 5 nm. possible process of pores diameter At the third stage (pores diameters - decrease as a result of polymer swelling. between 5 and 35 nm, time of etching - The swelling influence was valued by a 60-200 min) the intermolecular linkage correlation between the results of concentration decreases, the radial investigations of kinetics of etching for etching rate increases. two different polymer modes of At the fourth stage (pores diameters - treatment. In one case the polymer film above 35 nm, time of etching above 200 was transferred from one solution into min) the radial etching rate is constant another without drying, that is to say, if and is equal to the one of non-irradiated, the PI polymer swelled, pores diameters non-thermotreated PI film Vr = Vb = 1 would be underestimated. In another case nm/min [11]. This means that the the pores diameters were determined high-energy ion influence on polymer is 82 A. 1. Vilensky et al,

Tablo 1, Form ol PI trnoK mombrnnoo pcroa (otehlng In hydrogon pcroxld ol torriporaturo 00°C)

Thickness Etching Diameters of pores No. fim; Ion time, on both sides RSC, % hour of films, fim 1. to ~AT 5 0.10/0.15 1.1 10 0.29/0.41 10 Ar 5 0.10/0.20 0.6 10 0.20/0.57 2. 10 Kr 5 0.15/0.30 J.I 10 0.46/0.53

3. 20 Kr 5 0.35/0.40 1.1 10 0.65/0.65 4. 20 Kr 10 0,38/0.45 0.6

limited by the radius of 35 nm. a ion diminishes, decreases. In such a From the proceeding, the pores manner the polymer etching rate changes forming in PI track membranes can be along track what is reflected by the presented in the following way; polymer departure of pores shapes from cylindric completely destroys under irradiation in form. Figure 4 shows the relationship of the space of high-energy ion track (radius Ar, Kr and W ions energy losses dE/dx to below 5 nm) with the formation of ions range, x in polymer (with density ofp low-molecular products which are easily -1.4 g/cm ), which were caluclated on the being removed from the track zone. base of work [14] data for initial energy of Around the zone there is formed a space ions, used in this study. up to 15 nm in diameter where polymer The W ions range in polymer is structure is changed and where chemical approximately 9 fim, dE/dx is a resistance is increased. Further the monotonously diminishing function. The fraction of polymer with the changed Kr ions range is 30 fim. If the irradiated structure is reducing, and beyond 35 nm film thickness is 10 /urn, dE/dx is a the material does not differ from monotonously increasing function; if the non-irradiated polymer. thickness is 20 fim - the inlet energy losses A formation of space of increased correspond the outlet one. The Ar ions resistance makes it possible to obtain range reaches 12 fim, the dE/dx is track membranes for ultrafiltration (with asymmetric about the film surface. Thus pores diameters approximately 10 nm). in such conditions the films with thickness It is well known that the track etching of 10 ^am are expected to have pores of rate is connected with the energy losses of conic form, with 20 fim thickness and if ions, dE/dx. These losses are a irradiated by Kr ions - to have pores of non-monotonous function of ion energy surface close to cylindric form. E. Passing through the polymer, the high Table 1 lists values of pores diameters energy ions loss their energy and slow measured on different sides of PI film for down. As this takes place, the values of different conditions of irradiation and dE/dx first increase, go across the treatment. Figure 5 shows a maximum, then, as the effective charge of microphotograph of membranes breaks Tracks of hlgh-cncnry ions In. 83

Fig. 4. Tho rotation of onorgy losoos dE/dx for the Ar, Kr, W Ions to range In polymer (denaHy p • 1.4 g/cmn). The Initial Ions energy: 40 MoV (Ar), 220 MoV (Kr) and 55 MoV (W). Number on curves aro the Ions energy values (In MeV) In the corresponding points

makes possible to obtain track membranes with pores diameters of with pores of cylindric form (diameter - about 10 nm for ultrafiltration. Due to 1.2 fim). high selectivity of etching in H2O2 the For 10 fim thick films, the formed track structure appears also when they pores are of characteristic conic form. As form pores of big diameter. Therefore, they are etched, pores diameters on changing the energy losses of ions, different sides of the film equate, so the thickness, PI specification, and conditions cylindric form is characteristic for big of treatment in hydrogen peroxide, one pores. The pores form practically does not can obtain TM with pores of desired differ from cylindric if PI film with forms (cylindrical or conic). thickness of 20 jum is irradiated by Kr ions. REFERENCES 1. Fisher B.E., Spohr R. Reviews of 4. CONCLUSIONS Modern Physics., 1983, Vol.55 No.4, Thus, the following picture of pores pp.907-948. formed and etched in PI can be imagined. 2. Marenny A.M., Dielectric track As a result of high-energy ions passing the detectors in radiative-physics and polymer through they form some latent radiobiology experiment., M., tracks, which are characterized by imide Energoatomizdat, 1987, p.182. rings destruction in the central part with 3. Luck H.B., Nucl. Instrum. and Meth. radius up to 5 nm and by forming of Phys. Res., 1983, V. 213, pp.507-511. polymer with changed structure for the 4. Apel P.U., Didyk A.U., Kravets LI., remote zone with radius up to 35 nm. The Kuznetsov V.I. Orelovitch O.L. rate of etching of the central part by Dubna, 1984, Preprint P12-84-773. hydrogen peroxide (concentration 30 %, 5. Vilensky A.I., Oleinikov V.A., temperature 90 C) is high enough and Mchedlishvili B.V., Chemistry of high along the track reaches Vt -1000 nm/min; energies, 1992, Vol.26, No.4, pp.12-16. the etching selectivity is V = Vt/Vr = 6. Durrany S.A., Bull R.K., Solid State 2000. The density of polymer peaks at a Nuclear Track Detection Principles. radius of 5-15 nm causes high chemical AERE, Harwell, UK, Pergamon Press, resistance of polymer in this zone. This 1987. 7. Apel P.U., Berezkin V.V., Vasiliev 11. Vilensky A.I., Oleinikov V.A., A.B., Orelovich O.L., Zagorski D.L. Kuptsova I.V., Markov N.G.,Gusinsky Colloidal magazine, 1992, Vol.5, No.4., G.M., Mchedlishvili B.V., Chemistry j.220-223. of high energies, In press. Somaki Y., Matsumoto V., Ishikawa 12.Bessonov M.I., Polyimides - a new N., Sakurai T., J. Polymer class of thermostable polymers. L., Communications, 1989, V.3, No.2, Nauka, 1983, p. 307. p.43. 13. Barteniev G.M., Karimov S.N., 9. Patent Japan No. N61-83235. Narzullajev B.N., Kabilov Z.A., 10. Vilensky A.I.,Markov N.G., Oleinikov Matvejev V.K., Sarmina V.I., V.A.,Kuptsova I.V., Kushin V.V., High-molecular comp., A, 1977, V.19, Blinov V.F., Dontsova E.P., Zagorski No.10, pp.2217-2223. D.L., Nesterov N.A., Plotnikov S.V., 14. Northcliffe L.C., Schilling R.F. Chemistry of high energies., In press. Nuclear Data Tables, "970, Section A, Vol.7, No 3-4. TEMPERATURE EFFECTS IN POLYIMIDES IRRADIATED BY HEAVY IONS

L.I.Samoilova, P.Yu.Apcl, I.E.Larionova

Flerov Laboratory of Nuclear Reactions Joint Institute for Nuclear Research, Dubna, Russia

Abstract. The thermal stability of heavy ion latent tracks in polyimitlcs in the temperature range of 100°C to 300°C and the temperature effect during the irradiation in temperature interval of -180°C to 20°C are investigated. The chemical etching of the latent tracks was carried out in H2SO4 solutions containing potassium bichromate or in NaOCl (8% CI) solution. Experimental results showed that tracks in PI are resistant to high temperatures and the track formation is scarcely affected by the temperature during irradiation.

(produced in the former Soviet Union) 1. INTRODUCTION with the thicknesses of 'i! fim and 40/im - Compared with other polymer films, were irradiated by accelerated krypton polyimides (PI) are characterized by high ions with the energy of ca. 5.5 thermal and radiation stability and good MeV/nucleon from the GANIL and mechanical, electrical and chemical xenon ions with energy of 1 MeV/nucleon characteristics. These significant on the U-300 cyclotron. Irradiated films advantages allow one to consider PI as a were annealed at different combinations prospective material for the production of of temperature and time (see Table 1). track membranes and nuclear track The exposed films were etched with a detectors. solution on the basis of 16N H2SO4 and As it is known, the mentioned potassium bichromate (50 g/1) at properties of polyimides are connected temperatures of 90°C to 100°Q After with rigid-chain structure of their etching the samples were investigated by macromolecules. One can expect that a scaning electron microscope JSM-840 latent tracks in polyimide can also be (JEOL). characterized by high thermal stability The other series of samples of 7.5 fim and, more generally, by insensitivity to the thick Kapton films was irradiated by temperature at different stages of collimated fission fragments from the formation and existence of tracks. U-235 target at different temperatures In this paper we present the results of lying in the range of -180°C to 20°C (-180, two series of experiments performed with -170, -160, -150, -140, -120, -110, -70, -50, the aim to investigate: i) the effects of -30 and 20°C). The uranium target was high temperature annealing on latent exposed to the thermal neutron flux (10 heavy ion tracks in PI; ii) the influence of cm s' ) from a nuclear reactor. The track the temperature during irradiation on the density in the samples was ca 10 cm" . etching properties of the tracks. The conductivity of the samples was measured at 70°C in the solution of 2. EXPERIMENTAL NaOCl (8% CI) which served as etchant The polyimide films - 50 fim thick and electrolyte simultaneously. The Kapton (produced by Du Pont) and PM-1 conductivity data were converted into the 86 L. I Samo/Iova c( al.

Table 1. Results of IHS thermul annealing of hcuvy Ian tracks In poiyJrnidos

Temperature Time, h Type of Pl/projectilc Result

170" 18 12^m PM-l/Kr yes 40,umPM-1/Kr yes 200° 6 12,«m PM-l/Xc yes 300° 6 12/tm PM-l/Xc yes 6 12 ftm PM-l/Kr yes 6 50 fim Kapton/Kr yes 330" 6 12 A*m PM-l/Kr yes/no 6 SO/

values of effective pore diameter. The film. On the other side there were sample surfaces after etching were observed only surface pits. All types of observed by SEM. the examined polyimides showed short conical tracks after the treatment at 3. RESULTS AND DICOSSION 400°C during 60-90 minutes. At the 3.1, Annealing of heavy ion tracks at high longer time of annealing the tracks are temperatures faded completely. It was shown in the paper [1] that Xe tracks in PI seemed to be not faded in the The electron photomicrographs (Fig. temperature range of 100°C to 300°C at 1) show that there exist the domains with short annealing time (2-3 hrs). In the significantly distinct responses to the present work we extended the range of annealing. The etched pits having a broad annealing time and temperature. Since we variation of pore diameters and cone expected complete fading of tracks at the lengths are seen on the surfaces of the temperatures close to the highest service samples subjected to heating. Along with temperature of PI (400°) the testing of the tracks strongly faded one can find etchability was performed in the 'yes/no' some tracks which almost were not mode. Table 1 illustrates the results of changed in comparison with the reference experiments carried out for two types of sample (photo in Fig.l,a). This may be polyimides, two types of ions and various conditioned by the inhomogeneity of the conditions of annealing. Figures 1 and 2 virgin polyimide [3]. A significant show the surfaces of PM 1 and Kapton straggling of the experimental data did after annealing and etching. not allow to measure the parameters of the etching behaviour of annealed As can be seen from Table 1, partial polyimides and give quantitative fading of latent tracks is observed even at description of the track-fading. But, the 330°C (after 6 hrs annealing of PM-1). overall trend observed for all types of Exposure of 50,am thick Kapton at 360°C polyimides is the decreasing sensitivity of during 3 and 6 hours leads to complete polyimides with increasing exposure disappearance of tracks on one side of the temperature and time (the sensitivity is Temperature effects in., 87

Fig. 1. SEM photographs of the surface of a 12//m thick Pm-1 film annealed at 300° for 6 hrs (a), 360° for hrs (b), 400° for 1.5 hrs (c) and the reference sample (d).

the ratio of track etch rate to bulk etch linear function. Linear segments of the rate). Def vs t dependencies look like regular 3.2. Registration temperature effect in enlangement of perforated tracks. In polyimides order to find out the origin of "irregular" During the last decade much work has segments on the initial parts of the been done on investigating the effect of conductivity curves, the SEM studies of temperature during the irradiation with the samples were performed. It was found the aim to improve charge resolution of that under etching the big holes in the polymeric track detectors [2]. In the polyimide film were developed. The holes present work we investigated a sensitivity are caused by defects having the size close dependence on temperature during to the thickness of the film used. Some of registration in polyimides. This subject is the defects are being perforated before of interest in respect to the problem of fission fragment tracks. Only after the enhancement of the sensitivity of Pis. etching time long enough the population The results obtained are shown in of particle tracks is transformed to a Fig.3. The Def vs t curves have number of through pores, which grow and nonmonotonic initial parts which contribute to the electrical conductivity. correspond to slow and irregular rise of From the comparison of linear the conductivity in time. But after about segments of the Deff vs t curves one can 10-15 minutes of etching the growth of the conclude that there is no essential effective pore diameter is described by a difference between the samples irradiated Fig. 2. SEM photographs of the surface of a 50 ftm thick Kaplon film annealed at 400°C for \ h (a) and the reference sample (b)

150- Registration temperature; a ooooo 20 ° 6 o irirtririt -30 ' •••DO -170 o 100- it 00 Fig. 3. Effective pore diameter Den as a £ c 00 function of the time of etching at different registration temperatures 0

0° • • ca o cr £00 400600 "'.800'' 1000 Etching time (s) at different temperatures. Therefore, in homogeneous physico-chemical contrast to the polymers investigated properties would give, probably, a unique earlier polyimide track detector seems to temperature-insensitive track detector. be insensitive to the registration temperature. REFERENCES

4. CONCLUSION 1. L.I.Samoilova, P.Yu.Apel, V.I.Kuznetsov, S.P.Tretyakova., 1. PI seems to be not sensitive to the International Workshop "Solid State variation of irradiation temperature in Nuclear Track Detectors and Their the range of -180°C to 20°C. Applications", Dubna, 1990, pp.33-36. 2. Heavy ion tracks in polyimide are 2. D.O'Sullivan and A.Thompson. very stable at elevated temperatures. In Nuclear Tracks. 1980, v.4, No.4, comparison with other polymeric pp.271-276. detectors polyimides show extreme 3. Poliimidy - klass termostoikich thermal stability of latent tracks. polimerov. / Ed. M.I.Bessonov/. 3. The response of PI to annealing is Akademia Nauk SSSR. 1983, essentially inhomogeneous. The Leningrad, "Nauka". manufacture of a polyimide film with SELECTIVE AND CHEMICAL PROPERTIES OF POLYVINYLIDENEFLUORIDE TRACK MEMBRANES

V.V.Shirkova, B.V.Mchedlishvili , S.P.Tretyakova

Joint Institute for Nuclear Research Flerov Laboratory of Nuclear Reactions, Dubna *lnslitute of Crystallography, Russian Academy of Sciences, Moscow

During many processes of purification having been weighted and pore diameter and separation in chemically agressive has been determined before and after the media membranes obtained with the help treatment. Pore diameters have been of multiply charged ions from determined by means of the bubble polyethyleneterephtalate (PET) [l,2],and method and electron microscopy. The polycarbonate (PC),[3] are useless. The results of the experiment are presented in membranes of chemically stable polymers the Table 1. such as polypropylene and In order to study the influence of polyvinylidenfluonde (PVDF) can be chemical reagents on mechanical applied in a very wide region of properties and flow rate for the chemically agressive media. However, at PVDF-membrane samples (d=0.5 fim, present the PC- and PET-membranes thickness of 9 fim) having been treated in properties are given in details in literature four concentrated acids: HC1, HNO3, [4,5,6], but for the PVDF membranes H2SO4 and HF during 20 days at the there are no such a data. room temperature. To compare stability In this work the chemical stability of of the investigated membranes the the PVDF- track membranes and PET- PET-membranes of 10 fim thickness and membranes and their selective properties pore diameter of 0.72 fim were under *he have been investigated. The PVDF track same conditions. Mechanical resistance of membranes were prepared from the film samples has been determined by of 9 fim in thickness of the Japan destruction pressure. For this purpose production (Kurecha Chem. Ind.) by washed and dried sample of 1 cm square method described in the work [7]. has been subjected to the influence of The influence of chemically agressive increasing pressure and the moment of matters has been defined by changing the sample collapse has been fixed [6]. The sample weight and membrane pore productivity of the membrane samples diameter. For this purpose membranes has been determined by air consumption with pore diameter of 0.8 fim having been through 1 cm membrane at a small treated during 30 days at 80°C and at pressure drop (0.1-0.2 atm). The results room temperature in different chemical are presented in the Table 2. reagents. Washed and dried samples From this Table one can see that the Table 1 Reagent 20°C 80°C changing changing weight, % diam.,yum weight, % diam.,/mi NaOH, 20% not changed -1.1% 0.05 NH4OH (cone) ditto -2% 0.05

H2SO4 (cone) ditto 0.6% not changed

HNO3 (cone) ditto 2% structure is broken, cracks

HF (cone) ditto not changed

H3PO4 (cone) ditto ditto HCL (cone) ditto ditto *N204 ditto ditto

Cl2 ditto - ethyl alcohol ditto - Ethylen glycol ditto - Trichloroethylcne ditto - Toluene ditto - Hexane ditto - Benzene ditto - Tetrachloromethane ditto - * That was tasted at the INP of tho Belorusslan Academy of Sciences in order to study the possibilities of tho PVOF track membranes for purification of the N2O4 coolant.

Note: The PVDF is soluble in dimethylformamid, dimethylsulfoxlde, dimethylacetamide, primary amines (e.g. bytylamino), in ketones it is significantly swollen. Therefore, the PVDF track membranes are not applied in these solvents.

Table 2

Material Parameter Rough H2SO4 HNO3 HCL HF sample (91%) (56%) (35%) (48%) Airflow 140 fully fully 410 380 rate destr. destr. (1/h/atm/cm2) PET breaking 2.4±0.12 - - 1.4±0.12 2.6±0.12 point (atm) Air flow 440±35 400±35 - 440±35 - rate (1/h/atm/cm2) 570±35 - 560±35 - 605 ±35 PVDF breaking 0.75 0.83 0.70 0.80 0.57 point ±0.12 ±0.12 ±0.12 ±0.12 ±0.12 (atm) Selective and chemical... 91

Table 3 Material Sample Control sample Treated by HCL samples orientation Pn £% Pn E% MPa MPa Initial lengthwise 13.3 175.0 165.6 film ±1.3 ±12.0 ±15.0 across 21.0 57.0 260.0 ±1.2 ±6.0 ±16.0 lengthwise 3.2 12.7 46.0 3.5 14.0 49.0 ±0.5 2:3.1 ±8.0 ±0.6 ±2.0 ±5.0 D=0.35/

Fig. 1. Retention coefficient (y>=1-Cp/C0

where Co and Cp matter concentration in the original solution and permeat, ±0.05 versus (a) particle size and the PVDF track membrane pores relationship. They has been obtained for virus particles CMtV (d=0.03 fim), rabies virus (d=0.1 x 0.2 fim), influenza virus (d=0.13 fim), polyomieliiic virus (d = 0.025 /tm), diareja (d = 0.11 fim), and AIDS virus (d = 0.1 fim). The PVDF track membranes with pore sizes 0.2±1.5/

PVDF-membrane fully preserves its sample width is 10 mm, thickness - 9 fim. properties in all acids used while the The samples have been selected across PET-membranes either have been fully and lengthwise as the film probably has a broken or changed essentially their different degree of orientation in two characteristics. directions and tensile characteristics Mechanical properties of the samples should differ in two directions. The results of the PVDF track membranes (D=0.35 are given in Table 3. and 0.5^m, N = 3 x 10 ions/cm ) endured One can see from the Table that after during 20 days in 35% HQ at the room prolonged treatment in HQ the temperature have been additionally mechanical properties of the PVDF track investigated in the tensile testing machine membranes practically are not changed. INSTRON. Samples deformation (e,%) Selective properties of the and breaking point (rj,MPa) have been PVDF-membranes have been determined for control and for washed investigated in the processes of filtering and dried samples. the rigid colloid virus-particles (see fig.l). The speed of tension is 100 mm/min., As for the PET-membranes the selectivity of the investigated microliters has 3. FleisherR-L., PriceP.B. and depended on the dynamical conditions of WalkerR.M. (1975). NuclearTracks in testing (of tangent particles speed along Solids. Principles and Applications. the membrane and effective difference of Univ. of California Press, Berkeley pressure [8,9], The membrane pore size is (1975). chosen for the processes of prefiltration 4. Catal. Lab. 50 Nuclepore 0p=0, A<0.2) or concentration (p=l, A > Corporation, Pleasanton, 1980. 0.5-^-0.8) on the basis of analysis of such 5. Life Science Filtration Catalog, curves. To eliminate biocolloid Costar, 1992. adsorption the PVDF-membrane has 6. Booklet Nuclear Tracks Membranes, been modified by polymers seeding. Dubna, JINR. 19S9. 7. TretyakovaS.P., ShirkovaV.V., REFERENCES et.al.,Nuclear Tracks, Vol.12, Nos.1-6, 1. Flerov G.N., Barashenkov V.S., pp.75-76,1986. Uspekhi fizicheskih nauk, 1974, v.144, 8. Cherkassov A.N., MchedlishvilliB.V. p.351. et.al., Colloid Jornal, V.XL, N 6, 2. Flerov G.N., Bulletin of Academy of pp.1155-1160,1978. Sciences of the USSR, 1984, No 4, 9. MchedlishviliB.V., FlerovG.N. p.35. Journal of the Ail-Union Chemical Society, v.XXXII, N 6, pp.641-647, 1987. CREATION OF POROUS STRUCTURE ON CORUND SURFACE

A.E. Smirnov, D.L. Zagorski, G.N. Gusinski, V.T. Alshits, B.V. Vfchedlishvili

It is well known that traditional polymer track membranes may be used at low temperatures. So creation of high-temperature membranes is of great interest. One of the main problem is choosing material and its etching. In this work we used thin crystals of Corund (a -AI2O3), which possess rather high melting temperature (2000°C) and chemical stability. Next step was etching of the sample and creation porous structure on Corund surface. In our early articles [1,2] we proposed so-called "thermo-chemical Fig. 1 dissolution" of Corund. This process is reaction of Corund with carbone oxide during the high-temperaure heating. "marked" crystals at the atmosphere of Chemical reaction in this case can be CO. Then we investigated etched surface schematically written as: of crystals at the scanning electron 2 AI2O4 + 12 CO -» AI4C3 + 9 CO3 microscope TESLA BS-340. Thermal This reaction leads to solving of evaporation of (Ag) in vacuum was Corund surface. Varying etching used for creation thin conditions (heating time and electrical-conductive layer on the surface temperature, crystallographic orientation) of samples. we can change the microrelief. Different position of samples in We used mechanically polished microscope and changing of samples samples of Corund (non-oriented orientation during microscopic crystals) and irradiated by Ar-ions (with investigation gave us an opportunity to the energy 1 MeV/nucl.) "to mark" them, make space image of crystal surface. i.e., to make preliminary destructed areas. Microphotography is presented in Fig.l. Next step was chemical etching of these Pores were rather different in size and 94 A. E. Smirnov et al. had average size: length 20-40 //m, width for creation atomicly-smooth secondary 8-10 /.im and depth 5 /

D.Root, LXawton, H.Lane, K.Casey, J.Clements

Costar Corporation, USA

Abstract. The use of PTM for epithelial cell culture enables the cells to perform many of the functions in the laboratory that they preform in the intact living tissue. The basic properties of the PTM of thinness, uniform straight through pores, and a smooth top and bottom allow the cells to grow on top of the membrane and mimic their functions in a living organism. The cells can assimilate and transport a variety of molecules through the smooth pores of the PTM. The surface of the PTM is modified so that the cells may tightly attach to the top facial surface of the membrane. The specific properties needed for various cell culture applications will be reviewed and the methods of quantifying these properties will be presented.

CHARACTERIZATION OF 0.1 MICROMETER AND SMALLER PORE SIZE MEBRANES FOR BIOLOGICAL APPLICATIONS

D.Root, B.Green, J.Clements, C.Macomber, K.Bates

Costar Corporation, USA

Abstract. The use of small pore size PTM for biological applications is well documented. Pore diameters can be made to closely match the size of biological macrorrtolccules and small biological particles such as viruses and liposomes. The close matching of pore sire to the molecule to be separated enables separation of molecules with minor differences in size or charge. Driving forces such as electrophoresis can be used to separate molecules by charge because of the thinness of the PTM. The monolithic pore size distribution of PTM compares favorably with traditional cast membranes. The current literature will be reviewed and data presented for biological applications to demonstrate the separation properties of PTM with pore size 0.1 micrometer and smaller.

APPLICATION OF ION TRACK MEMBRANES FOR PREPARATION OF METALLIC NANO- AND MICROSTRUCTURES

J.Vetter

GS1, Darmstadt

Abstract. Polymer membranes or mica sheets with etched particle tracks can be used not only as filters but also as matrices to produce microwhiskers. A thin metallic layer is sputtered on one side of polymer membrane. In an electrolytic bath pores smaller than 1 fim in diameter, and up to about 100 pirn long, are filled with metallic or conducting organic material. A structure composed of parallel conducting threads imbedded in insulating material is thereby produced. After peeling the polymer membrane from the metal substrate and after chemically dissolving the polymer free whiskers are obtained. Such structures with submicron diameters may be interesting objects for use in micromechanics. If the structured membrane is directly dissolved from the substrate, whisker-arrays of up to 1 cm2 can be produced. On the other hand, the shape of etched ion track channels is of great interest, but imaging of the channel interior by means of techniques such as SEM is not easy. However, due to the technique presented here the form can be investigated.

OPTICAL PROPERTIES OF STRUCTURE PREPARED ON THE BASE OF NUCLEAR FILTER TECHNIQUES. PREPARATION OF SUBSTRATES FOR TRACE ANALYSIS BY SURFACE-ENHANCED RAMAN SPECTROSCOPY

V.A.O!einikov, K.V.Sokolov, I.RNabiev, T.M.Cotton, R.A.Uphaus

Abstract. A set of flexible subslrates for trace organic analysis by surface-enhanced Raman scattering (SERS) spectroscopy is developed, comprising flexible support treated by ions irradiation, chemically etched and coated by silver. Also a procedure for using the mentioned above substrates in the picogramme level SERS trace analysis, especially for biological, biomedical and related organic compounds was developed. This new type of SERS-active surfaces has been characterized by UV-vis reflection spectroscopy, electron and scanning tunnel microscopy, and optimized for the maximum Raman cross-section enhancement factors. SERS spectra of some biological molecules on these SERS-active surfaces have been recorded from the piccgrammes of the samples. The data confirming long-range electromagnetic mechanism of Raman spectra enhancement has been presented.

defined by electromagnetic field 1. INTRODUCTION enhancement near the surface, and does Surface-enhanced Raman not depend on the nature of adsorbate. In spectrometry (SERS) has recently its turn, electromagnetic mechanism received considerable attention as a new enhancement is defined by a local field technique for analytical and structural enhancement near the surface and analysis of organic molecules [1,2L especially near the protrudings on the Enhancements by factors of 10 to 10 surface. This enhancement is caused by can be realized in Raman scattering resonant plasmon oscillation in intensity of adsorbates on or near special protrudings, as well as by non-resonant rough metal surfaces. This phenomenon enhancement effect defined by field has been verified for adsorbates on silver, enhancement near high curvature surface copper, gold, platinum, aluminum and (lightning rod effect). That is why otuer surfaces under both solution and researches into the field of creation of vacuum conditions. These spectacular surfaces with prolated protrudings which enhancement factors help to overcome are resonant in a desirable band and the normally low sensitivity of Raman having sharp microneedles or edges spectroscopy which had often necessitated allowing an additional enhancement by the use of powerful, costly laser sources lightening rod effect (two scale for excitation. protrudings) are important. There are two mechanisms of Raman Heretofore, rigid surfaces were scattering enhancement: molecular prepared for SERS via a variety of short-distance) and electromagnetic techniques, such as electrochemical long-distance) mechanisms. The first roughening of electrode surfaces, one, molecular, is caused by forming lithographic or chemical etching, the strong interaction between adsorbate and "prolate post" method, the method of adsorbent. Consequently, it depends on deposition of roughness-imparting surface propertiesas well as the nature of microbodies and the silver hydrosol adsorbate. The latter, electromagnetic, is method [3-5], None of the mentioned above method;; Irradiation was performed on cyclotron give the possibility to create the U-400 (JINR, LNR, Dubna, Russia) by structurized surfaces with two scale Ar, Kr, Xe ions with energies 1-3 protrudings. A reliable way to create this Mev/nucleon, surface density up to 10 type of surfaces is using track membrane cm" . technique [6], Polyethyleneterephthalate (PETP) foil was used. Etching was performed in water 2. EXPERIMENTAL TECHNIQUE or water-alcohol solutions of KOH or Raman-active structurized surfaces NaOH at concentrations of 0.1-5 N and (substrates) were synthesized as replicas temperatures of 20-90uC. on track membranes surface. For this Metal was deposited in a vacuum on purpose the track membranes with foils prepared in such conditions. cylindrical or conical pores or foils with Thickness of the layer deposited was conic microcavities on their surfaces were 100-1000 nm. Such as Ag, Au, Cu, prepared. Geometrical parameters of Al, Cr, Mo were used. If necessary, pores and microcavities, their diameter thickness of the metal layer was increased and depth depend on conditions of high by means of electrolysis. A bath with energy ions irradiation (on mass and sulfuric electrolyte coppering was used. energy of ions), conditions of chemical Thickness of copper layer was 3000-10000 etching (concentration and composition nm. of solution, temperature and time of After described above procedure treatment) and they can be variable in PETP foil was removed mechanically or wide ranges. A surface density of chemically (water or water-alcohol microcavities is determined by dose of solutions of KOH or NaOH were used). irradiation of initial foil with fast ions. The samples of the tested compounds

Fig. 1. Raman-spectra: 1 — SERS-spectrum of lysozime adsorbed on silver electrode surface in electrochemical cell, sample is 1pq; 2 — SERS-spectrum of lysozome deposited on the surface of protrudings structure (d = 30 nm, surface density of protrudings is 1011 cm"2), sample is 1 pq; 3 — Raman-spoctrum of lysozyme in aqueous solution at concentration 25 mg/ml; 4 — SERS-spectrum of phenylalanine deposited on th9 protrudings structure, conditions are same with (2). Wave-lenght of excitation is 514 nm, for SERS-spectra (t, 2, 4) the power is 10 nW, for Raman-spectrum (3) the power is 250 mW

1500 500 LV.CM"1 Optical properties of. 103 were adsorbed on the substrate by in an electrochemical cell (short-distance deposition of 1 //I of solution onto the in comparison with chemical bond substrate. 514.5 nm laser excitation with length). power 10 mW from Spectra-Physics, An opposite situation is observed for model 164-03 argon ion laser have been SERS-spectra of lysozyme deposited on used for recording of the SERS spectra. protrudings surface prepared by means of The laser beam was focused up to 1 /urn track membrane technique. In this case diameter using microscopic objective the observed spectrum practically does (Olympus BH-2). In all cases there were not differ from Raman spectrum of 0.1-1.0 pg of the tested compound under lysozyme aqueous solution, though it is the laser beam. registered at concentrations of 3 orders lesser. This fact is an evident argument, 3. RESULTS AND DISCUSSION which proves that long-distance SERS-spectra of a number of colored electromagnetic mechanism of compounds (Rodamin-6G, enhancement is the main factor in this tetraphenilporphin zink) as well as process. transparent ones In conclusion it is necessary to say that (phenylalanine, 4,4-bipyridine, adenin, the use of SERS-active surfaces, lysozyme) were got. It was found that prepared by means of track membrane surface density of protrudings is the replicas technique allows to record critical parameter for Raman scattering SERS-spectra beginning with enhancement of all studied compounds. picogramme quantities of compounds Decreasing of protrudings sizes and rising with various chemical nature. Thus, of their surface density allows to SERS-active system suggested here is maximize Raman scattering universal. The main mechanism of enhancement. It gave the possibility to enhancement is electromagnetic record Raman-spectra of compounds in (long-distance). It can be effectively used picogramme amount. to increase sensitivity for Raman-spectra Spectra of lysozyme are presented in registration. Fig.l: (1) shows SERS-spectrum of this protein adsorbed on silver electrod REFERENCES surface in electro-chemical cell; (2) — 1. Surface Enhanced Raman Scattering. SERS-spectrum of the protein deposited Edited by R.K.Chang & Th.E.Furtak, on the surface of a protruding structure Plenum Press, New York & London, made by means of track membrane 1982. technique; (3) — Raman-spectrum of the 2. Nabiev I.R., Efremov R.G., protein in an aqueous solution; (4) - Chumanov G.D., Uspekhi Fiz.Nauk, SERS-spectrum of aromatic amino acid 1988, V. 154, N.3, pp.459-496. phenylalanine on the protruding structure surface. 3. Cotton T.M. In the Book: "Spectroscopy of Surfaces. Advances The most intensive bands in SERS in Spectroscopy. Vol.16". 1988, John spectra of lysozyme, adsorbed on silver Wiley & Sons Ltd., pp.91-153. electrode, correspond to oscillations of 4. Liao P.F., Bergman J.G., Chełma D.S., aromatic amino acid residues of this et al., Chem. Phys. Lett.,1981, V.82, protein. It should be mentioned that p.355. bands of characteristic oscillations of 5. Vo-Dinh T., Hiromoto M.Y.K., Begun phenylalanine residue are absent in 1000 G.M., Moody R.L., Anal. Chem., cm" region. Lysozyme molecule is of 1984, V.56, N.9, pp.1667-1670. ellipsoid shape with sizes of 45x30x30 A 6. Asadchikov V.E., Zagorskij D.L., and contains three phenylalanine Mchedlishvili B.V, et al,Proc. of the residues. Nevertheless, signals of the 2nd Meeting "Particle Track residues, localized inside the protein Membranes and their Application", molecule, practically do not appear as the 1991, Szczyrk, Poland, Warsaw, 1992. process providing Raman-scattering enhancement on silver electrode surface

APPLICATION OF PARTICLE TRACK MEMBRANES IN GLUCOSE SENSORS

I. Zawicki, M. Buczkowski

Institute of Biocybemetics and Biomedical Eng. Polish Academy of Sciences, Warsaw •Institute of Nuclear Chemistry and Technology, Warsaw

1. INTRODUCTION 2. PRINCIPLE OF OPERATION OF THE Among chemical sensors, enzymatic ENZYMATIC GLUCOSE SENSOR glucose sensors also called biosensors, Principle of operation of the glucose have reached high level of development. sensor is shown in Fig.l and a layout of the The main demand for glucose sensors pical amperometric biosensor based on comes from medicine. A need of quick g2 detection - in Fig.2. measurements of glucose level in blood is The essential components of the connected with diabetics. Nowadays glucose sensor are following: diabetesis has been a big social problem. • a semipermeable membrane containing For example from this disease suffers: immobilized glucose oxidase enzyme

0.3% of population in Japan, 1.5% - in (GOx), a detecting system containing: Poland, 4% - in the USA. Many efforts have been undertaken for developing a closed loop artificial Fig. 1. Principle of operation of the amperometrie glucose pancreas system which includes glucose biosensor sensors. Such sensors should, preferably, be implantable or noninvasive. So far this Sample Membranę) Detection goal has not been reached. Also in food Outer ł inne^ r processing, agriculture, and modern ł lEnzy- I l biotechnologies there is the need for | jmatlo simple methods of glucose measurements. A glucose sensor can be also a basic component for some methods of H2°2 measurements of the concentration of or such sugars as: lactose, maltose, or 0„ sucrose. The required measurement range of glucose biosensors should be following: 50 • 500 mg/di for medical application GOX G + 0 + H 0 ---^Gluc.aoid 4- H 0 and 0 -1000 mg/dl for other applications. 2 2 2 2 i . R„ depends on: construction, geometry, technology, and operating conditions of biosensors. - - One possible way of controlling the linearity of the range of a sensor can be u immobilization of glucose oxidase (GOx) -fi + within membrane material of different permeabilities for glucose. Working aleotrods 3. APPLICATION OF PARTICLE TRACK Jieferance elaotrode MEMBRANES IN BIOSENSORS 3.1. Standard membranes Innsr aleotrolyte /0.1 N KC1/ Taking into account above suggestions, investigations have been undertaken to applicate of particle track membranes (PTM) in biosensors. These membranes were prepared of polyester, polycarbonate, and polypropylene foils. In the first case Polish polyester foil Estrofol "2 " "2 has been used. The thickness of these S • • p 1 i membranes have been in the range 8-15 Fig. 2. Essential components of the glucose biosensor fim. [1,3]. PTMs were used as the outer • a working electrode, a reference membranes in the glucose biosensor". electrode, and inner electrolyte. A Pore sizes of these membranes were: 0.1; voltage supply is connected to the 0.22; 0.3; 0.45; 1.0; 1.2 /um, and porosity - electrodes in series with a resistor - Rd. in the range of 6 -12 %. Glucose (G) and oxygen (02) which The results obtained with some of are present in a sample react within an above membranes are shown in Fig.3. The enzymatic membrane producing H2O2 curves in this figure show the output and gluconic acid. The amount of oxygen voltage of the sensor vs glucose reaching the working electrode depends concentration for various PTMs applied in on the concentration eg of glucose in a the biosensor. As a reference membrane sample. The higher eg the smaller is the Cuprophan routine membrane was amount of oxygen at the working used. An increase of the linear range in electrode. The output signal Ud is directly most cases with PTMs is seen. related to the partial pressure of oxygen at the working electrode. This relation vs eg is following:

Ud = ki • P02 = ki • (max P02 - *2 • cg) (1) Fig. 3. Measurements ranges of the glucose biosensor for where: k2 and kiare the experimental different outer membranes (pore sizes of PTMs are coefficients. indicated) The above relationship is linear in a ó' certain range of glucose concentration, BV CUPROPHAN i.e., as long as there is more oxygen than it is required for the reaction with glucose within the enzymatic membrane. In p. 3FIM samples saturated with air, the molar 20 ,1. Opn concentration of oxygen is frequently ,0. lpm much lower than the concentration of glucose. Therefore, without special efforts, the linear range of the glucose sensor is generally narrower than it is required in many applications. This range ó To 20 3o 7b iió 35 io" TINA, • Fig. 4, Response of the glucose biosensor for 2 different outer mombranes: a) — Cuprohan, b) — modified PTM

ml for Cuprophan membrane, is 3.2. Modified PTMs satisfactory for many practical As membranes of the lesser porosity applications. than 6 % were not available the increase of the linear range was rather moderate. 4. CONCLUSIONS Therefore, in further experiments The experimental results reported in modified PTMs were used with subtle the paper indicate that PTMs can be structure in micropores. Such membranes useful for application as the external are being investigated and prepared in membrane in amperometric glucose the Flerov Laboratory of Nuclear biosensors. Such membranes have Reactions, Joint Institute for Nuclear advantage over some other types of Research, Dubna. [2,3] routine membranes because they improve Modified PTMs membranes were used mechanical as well as metrological in experiments with N7U-k sensor. This properties of glucose biosensors sensor requires a sample of a drop size increasing their life time and measuring and its description is given in [4]. range. It was possible to increase twice Obtained results of transient responses of the linear range of the biosensor in N7U-k sensor are given in Fig.4. ( In comparison with the use of the routine Fig.4a results for Cuprophan membrane membrane. and in Fig.4b results for modified PTMs Particulary purposeful seems to be are given). The significant increase of the application of the modified PTMs with a sensor range is seen in case of modified subtle structure inside pores, developed PTMs. This difference illustrates Fig.5. and prepared in JINR Dubna. Such The increase in the useful range of the membranes can give significant (5x) sensor with modified PTMs up to 200 widening of the measuring range. mg/100 ml in comparison with 40 mg/100 It seems that futher improvement can 108 I. Zawicki ct al.

be achieved by using modified particle 2. N.J.ZhitamiklN.I.Zagaiets,v.l.Kuzne track membranes with lesser than typical tsov, Kinetics of radia- tion-induced value of porosity. graft polymerization of styrene onto Acknowledgments poly(ethyIene- terephthalate) nuclear The enzymatic membranes used in the membranes, in JINR Dubna Mat. experimental glucose sensors were 18.89.48,1989 (in Russian). obtained from Dr.M.Filipiak (Dep. of 3. Proc. of the 1st Meeting on "Particle Biochemistry and Microbiology, Academy Track Membranes and Their of Economics, Poznan). Applications", May.1989, Jaworze, Poland. Publ.: INChT, Warsaw 1990 Authors thank Dr. N.I.Zhitariuk from (in Russian). the Flcrov Laboratory of Nuclear 4. I.Zawicki, M.Filipiak, Z. Adamaszek, Reactions, JINR Dubna, for the J.Krzymień, R.Miarczyński, discussion and help in experimental part. Z.Szczepanik,M.Nałęcz, The experiments with PTMs were Electroenzymatic Glucose Sensor - carried out by Mr Mr R.Miarczyński and Results of Tests with Blood, Lecture Z.Adamaszek. The work was partially Notes of the ICB Seminars, Artificial financed from KBN Grant No 886529102. Pancreas and Drug Delivery Systems. Mądralin, April 1991.(Eds.: REFERENCES V.Shumakov and M,Nałęcz), Publ.: Int. Center of Biocybernetics, 1. Proc. of the 2nd Meeting on "Particle Warszawa, Poland, 1992. Track Membranes and Their Applications", Dec.1991, Szczyrk, Poland. Publ.: INChT, Warsaw, 1992. SOME CHARACTERISTICS OF SPIRAL AND PLATE MODULES

G. Dajko*, J.Toth**

institute of Nuclear Research of The Hungary Academy of Sciences, Debrecen, **Research Laboratory for Mining Chemistry of The Hungary Academy of Sciences, Miskolc

Abstract. Different spiral and plate modules, applying track membranes were investigated. The flow rates of modules were determined experimentally as a function of the pressure and the permeate-retentate ratio. Some of characteristics of modules were determined with calculations using experimental results.

PARTICLE TRACK MEMBRANES AS MINICONTAINERS FOR LIQUID CRYSTALS

J. Błądek*, A. Rostkowski**

•Military TGchnical Academy, Warsaw, Poland, **Academy of Telecommunication, Zegrze, Poland

easily be supercooled and preserves its 1. INTRODUCTION nematic structure even at 273K. 5 x 10 cm PT membranes show very strong pieces of PT membranes (pore diameter ordering properties to liquid crystalline 0.05 fim; thickness 12 jum, surface pore molecules. It means that impregnation of density 4.5%) were impreganated by porous foil with liquid crystal leads to direct application of the liquid crystal to formation of thin liquid crystalline layer the foil: filter paper was used to remove with ordered texture. Such textures show excess liquid crystal from the foil surface. anisotropy e.g. anisotropy of optical Before use the performance of the properties. This phenomenon appears in detector was checked by placing it on a linear polarised light as intensive polished (i.e. reflective) metal surface and interference colour layers. Of course, examining its appearance when disordering of the structure i.e. transfer of illuminated with linearly polarised light; liquid crystals to isotropic liquid degrades correct preparation was indicated by the texture. It leads to change or uniform coloration of the detector disappearance of colour. Because of that, surface. This colour, caused both by PT membranes impregnated with liquid birefringence, a characteristic of thin crystals were called liquid - crystalline layers of liquid crystal, and by detectors. These detectors are used for interference of light reflected from the temperature measurement and for metal surface, depends on the thicknes of detection of organic compounds, soluble the PT membrane (i.e. the thickness of in liquid crystal from which the detector is the liquid crystal layer contained in the prepared. Both of these parameters: pores of the membrane), the diameter temperature and/or admixture presence and surface density of the pores, and on can cause transfer of liquid crystal to the the orientation of the detector with isotropic liquid, what is visible as colour respect to the polariser. "answer" of detector. 0.2 - 0.8^1 quantities of 0.01 % solution 2. EXPERIMENTAL of the substance to be determined were The liquid crystal used for this study applied to the chromatographic plates was p-cyanobiphenyl (PCB), mesophase and the solvent evaporated. The spots range 296 - 310K. This compound can were mapped immediately by pressing the Fig. 1. Influenca ot the dosago volumes on the spot sharp: a — 04,4/

Fig. 2. Influence of the polarity of sample solvent: a— methanol, b— dichloromethane, c— hexane

Fig. 3. Influence of the adsoibent kind; a — cellulose, b— kleselgur, c —silica-gel detector on to the adsorbent surface The linear variation of liquid crystal (pressure 0.4 MPa; temperature 353 K; clearing point with concentration of time 3 min) using a device resembling the non-mesogene is a characteristic feature chamber used for over - pressured thin of nematic liquid crystal solutions and layer chromatography. The detector was points to the additive nature of the effects removed from the adsorbent, cooled to of both parameters (i.e. non - mesogene room temperature and placed on the concentration and temperature) on the heated stage of the polarisation disturbance of the degree of ordering of microscope. The clearing points of the the liquid crystal structure. This is the binary systems obtained were then reason the spot of a substance mapped on measured and the concentration of the the liquid crystal detector appears at an non-mesogene in the liquid crystal accurately defined temperature determined from the standard curve. corresponding to the local composition of Particle track membranes. 113

Fig. 4. Changes of concentration distribution in spot vs the (time) migration distance: a — start lino, b — 3 mm, c — 10mm, d — 20 mm the mesogene - non-mesogene system. possibility to use of liquid crystalline This feature characterises the liquid detectors as investigation instrument in crystal visualization method; the detector thin layer chromatography which may does not reveal immediately the final verify any of chromatography theories. In shape of the spot as distinguished by this place, it is worth to underline those either optical methods such as none of these theories were confirmed by fluorescence, or the production of verification researches. coloured species by chemical reaction. Idea of liquid crystalline detector The lowest temperatures cause the application as investigation instrument appearance of colour only at small sites comes from to observe possibility of corresponding to the regions of the concentration - spatial geometry of highest concentration; as the temperature chromatographic spots or zones mapped is increased the spots grow as areas of on to detector. Such mapping may be lower concentration become visible. This realised at any distance of development is a consequence of heterogeneous and at any adsorbent. It makes possible to distribution of the spot on the adsorbent measure many parameters of surface, and occurs both at the origin and chromatographic process. after development. In Fig. 1 it is shown influence of spotted sample volume on spot shape. It 3. DISCUSSION is easy to see that just at the start line, Application of liquid - crystalline inital diffusion condition is difficult to detectors to the visualisation of thin layer estimate. Spot shape at start line depends chromatography as well as to the forensic on polarity of sample solvent (Fig. 2), as investigations were presented in literature well as on type of adsorbent (Fig. 3). [1 - 6]. However, these works seem to Disturbance in formulation of one of have less cognitive significance in boundary diffusion conditions seems to be comparison with recently observed reason of thin layer theory's imperfection. Concentration - spatial change of spot geometry in chromatographic process is REFERENCES presented in Fig. 4. In this case Gaussian 1. J.Błądek, J.Chromatogr., 405 (1987) concentration distributions, parameters of 203-211. which vary due to time development are 2. J.Błądek, J.Chromatogr., 437 (1988) visible. 131-137. Results of experiments confirm the 3. J.Błądek, J.Planar Chromatogr., 3 possibility of using the PT membranes (1990) 307-310. and a liquid - crystalline detector as a 4. J.Błądek, J.Moszczyński, researching instrument in thin layer For.Sci.International, 50 (1991) 87-96 chromatography. It maps a concentration 5. M.Miszczak, J.Błądek, Propel., - spatial geometry of spot, giving the Exp.,Pyrotechnics, 18 Q.993) 29-32. information about parameters of 6. J.Błądek, J.Planar Chromatogr., 6 concentration distribution and factor (1993) 487-491. influencing changes of these parameters dxiring a chromatographic process. APPLICATION OF TRACK MEMBRANES AS THE SEPARATING LAYER IN FILMY OXIDE CAPACITORS

G.Gusinsky, W.Gusev, L.Karpuhina

loffe Physico-Technical Institute of Russian Academy of Sciences St. Petersburg, Russia

The schematic diagram of filmy oxide the layer. The intermediate contact capacitor is shown in Fig. 1. The between the electrodes should be avoided. electrodes are made of Ta or Al foil. The oxide surface of the anode foil should Anode foil is oxidied by electrolytic be prevented from the cathode foil to method in order to receive thin dielectric avoid the destroying of this surface. Thus layer (0.1-0.2 /mi). A large capacity of the the electrolyte filled cellulose paper is capacitor results from small thickness of used as the separating layer between both electrodes. In order to obtain a large discharge Fig. 1. The schematic diagram of filmy oxide capacitor and FTM as separating material pulse current the capacitor must have the

small value of inner resistance Rs.

+ to C ox where: R - resistance of the separating layer,

<50| - angle of dielectric loses in oxide layer, Cox - capacity of dielectric layer. For the frequenceies co > 100 Hz the second part of the formule (1) is close to zero, and

Rs -R=p|

value caused by its transformation from the (about 10 Ohm-cm). The acid crystalline phase to the liquid phase electrolytes with p less of order of such under the action of the surface-tension magnitude cannot be used because of force their aggresive interaction with cellulose The change of the traditional paper paper. The capacitors containing neutral separating material on PTM increases the electrolyte filled cellulose paper can work price of the capacitor for 40% only, in narrow range of low temperatures. although the PTM price is for 200% The parameters of the capacitor higher than of the cellulose paper. This is mentioned above can be improved by connected with the low participation of using the PTM as the separating material. separating material cost in total capacitor For example in the case of 20 fim in cost which can be estimated as no more thickness electrode foil and 10 fim in than 1%. thickness of PTM the useful capacity of Now it has been prepared the pilot the capacitor increases 2-times in series of the capacitors with PTM comparison with the same capacitor with separating layer, but with neutral paper separating layer. electrolyte only. Application of acid The

B.Zelikson, B.Mchedlishvili, B.Basin, M.Gromov

JSC "Optica" Saint-Petersburg, Russia.

For the first time in Russia, the JSC in 30 minutes; duration of detoxication "Optica" has developed original design procedure up to 3 hours without and technology of production of flat considereable loss of MPF productivity. membrane plasmafilters (MPF). MPF has The unique peculiarity of this filter is successfully passed clinical field-tests and possibility to work without using the obtained permission for the use and special equipment; the bloodstream goes industrial production from Ministry of through the filter moved by gravitation Health Protection of Russia in 1992. force; in this case, mononeedle scheme is used, and the MPF provides separation of PTM are used because of the need in 150-200 ml plasma in 40 minutes and this procedures of plasmapheresis. procedure can be repeated. This Plasmapheresis (PP) is a process of peculiarity lets use the MPF in "movable" plasma separation from human blood. medical stations, for medical help in There are toxines in blood of a sick man: extremal situations, in catastrophe they can be removed together with medicine. plasma - it is a medicinal plasmapheresis (MPP). There are extremely valuable Among membrane plasma separators natural biological substances in blood of a the most popular now are devices based healthy man, which can be separated on so-called hollow fibres ("Plasmflo", together with plasma and injected to sick "Asahi" Inc, "Gambro", "Plasmoflex", people - it is a donative plasmapheresis "Fresenius", and so on) having sponge-like (DPF). structure. The same structure is also typical for membranes in flat-membrane The MPF is hemocompatible, devices ("Cobe Laboratories" Inc., "Fone hypohenic, non-toxic, sterile. Sterilization Poulene, "Sarns" Inc. and so on). Track is carried out by gamma-rays (2.5 Mrad). membranes possess a number of merits in For MPF production the track membrane blood fractioning. Here is meant first of is used; it is made of Lavsane film 10 all: lower traume of erythrocites, thick, with pores of 0.3-0.5 fim. Effective biological inertness, small sorbtion area. filtration area - 800 cm . Prelimanary While the last two parameters are evident filling volume - 15 cm .Transmembrane and elucidated in literature, the first one pressure is not more than 140 mm Hg. requires clarifying. The speed of blood flow- 30-60 mm/min. Plasma yield - no less than 30-35% of A.L. Zydney and C.K. Colton (1982) entering flow. Sizes - 130x75x6.5 mm. In have suggested a model based on condition of 2-needle scheme MPF principle that hemolysis is the result of provides: separation of 500 ml of plasma erythrocites deformation when cutting into membrane pores. In membrane module with the sodium chloride aerosol. plasmapheresis, the erytrocite rolls or This is non-destroying intelligent test slides along the membrane and passes when defects may be discovered with the over pores. It gets into a pore periodically special photometric equipment. and can be removed out off it by shearing We have official permission for clinical stress close to the membrane. Zydney and tests and use of our plasmafilters. You Colton have established (1982) that can see several examples of the critical transmembrane pressure (TMP) is plasmafilter application for detoxication not a stable value but depends on speed and correction of internal medium. of blood moving and diameter off Doctor V. Voinov proceeds the treatment separating membrane pores. of astma-patient in Pulmonology Institute The more the pores diameter, the with the prolonged plasmapheresis (3 more vivid are shearing stresses on hours, when 3 litres of plasma were erythrocite's membrane and this causes removed and alter specific sorbtion of appearing hemolysis. We have proved allergens the plasma was returned back experimentally that the significant merits into the patient blood system). in comparison with sponge-like membranes (from point of erythrocites Plasmafilters could be applied in the traume) are: lower porosity (approx.7%), scheme of the plasmapheresis procedure little deviations from nominal pore size without pumps. It is the simplest scheme, (3-5%) and more correct geometrical very convenient for urgent medicine shape (cylinder) of track membrane giving the flexibility. It may be used at pores. Influence of low porosity (7%) on home, in the forest, at any conditions the intensity of plasma flow are when the special blood-transfusion compensated by small membrane equipment is not in your disposal. thickness (10-8 /

• one donor can provide up to 50 Jitress 2. Mchedlishvili B.V., Flerov G.N., of plasma but not more than 2 litres of Jadernye filtry: novyj klass blood yearly; mikrofiltracyonnych membran v • unlike blood, plasma can be sterilized. precizionnom razdielenii kolloidnych This excepts the possibility of rastvorov, Zhumal VChO im. unfectioning by AIDS, hepatitis; Mendeleeva, 1987 v. 32,641-647. • the plasma of people who had 3. Nose Y., Malchesky P.S., Technical different illnesses, burns, inoculations aspects of membrane plasma can be used as a ready serum treatment, Artif. Organs, 1981, v.5 medicine. Suppl., 86-91. The MPF can be used for 4. Zydney A.L., Colton CK.., Continuous microfiltration in the biotechnology, flow membrane plasmapheresis: pharmacy, food industry. Theoretical models 'for flux and hemolysis prediction, ASAIO Trans., REFERENCES: 1982, v. 28,408-412. 1. Flerov G.N., Sintez sverhtiazolych elementov i primenieniye metodov jadernoj fiziki v smeznych sistemach, Vestnik AN SSSR, 1984, 4, 35-48.

RADIATION RESISTANT POLYPROPYLENE

J. Bojarski, Z. Bułhak, Z. Zimck

Institute of Nuclear Chemistry and Technology, Warsaw, Poland

Abstract. Polypropylene (PP) is used, among other application, for medical devices production. It was applied also for nuclear track membranes and nuclear track filters development beside other materials like polyethylene terephtalatc and polycarbonate. The various crystal structure of PP has significant influence on biaxially oriented PP films 10 fim thick formation, which is suitable to this application. Modified polypropylene (PP-M) has been obtained in the Institute of Nuclear Chemistry and Technology. This material can be used for production any kind of medical devices. Radicals which are form during PP irradiation are located in crystal phase (stable radicals) and amorphous phase (unstable radicals). Those species have fundamental influence on PP properties after irradiation process. The basic properties of PP-M are described in presented lectures.

LIST OF PARTICIPANTS (in alphabetical order)

1. AALTO Karri, Aalto Development Oy, Finland 2. APEL Pavel.Yu., JINR, Dubna, Russia 3. BEREZKIN Vladimir V.Institute of Crystallography, Moscow, Russia 4. BŁĄDEK Jan, Military Technical Academy, Warsaw, Poland 5. BOJARSKI Jerzy, Inst, of Nucl. Chcm. & Technology, Warsaw, Poland 6. BUCZKOWSKI Marek., Inst.of Nucl. Chem. & Technology, Warsaw, Poland 7. CIEŚLA Krystyna, Inst.of Nucl.Chem.& Technology, Warsaw, Poland 8. DAJKO Gabor, Inst.of Nucl. Res., Debrecen, Hungary 9. DIDYK Alexander Yu., JINR, Dubna, Russia 10. DMITRIEV Sergei N., JINR, Dubna, Russia 11. FERAIN Etienne, Univ. Catholique dc Louvain, Louvain-la-Neuve, Belgium 12. FIDERKIEWICZ Alfred, Inst, of Nucl. Chem. & Technology, Warsaw, Poland 13. GĄDOR Witold, Technical University of Łódź, Branch in Bielsko-Biała, Poland 14. GRACZYŃSKI Adam, Central Mining Institute, Katowice, Poland 15. GUSEV Vladimir, Ioffe Phys., Techn. Inst., St.Petersburg, Russia 16. GUS1NSKY Grigory M., Ioffe Phys.- Techn.Inst., St.Petersburg, Russia 17. HARASIMOWICZ Marian, Inst, of Nucl. Chem. & Technology, Warsaw, Poland 18. HEINRICH Berndt, IIM, Rossendorf, Germany 19. HUBBARD Eugene T., Poretics Corporation, Livermorc, USA 20. KIEŁKIEWICZ Jędrzej, Warsaw Technical University, Poland 21. LEGRAS Roger, Univ. Catholique de Louvain, Louvain-la-Neuvc, Belgium 22. LUKEZIC Stan, Poretics Corporation, Livermore, USA 23. MAGDZIORZ Antoni, Central Mining Institute, Katowice, Poland 24. MEINHARDT Bolesław, Central Mining Institute, Katowice, Poland 25. MEINHARDT Elżbieta, Central Mining Institute, Katowice, Poland 26. MICHAŁOWSKI Jan, Polish Copper SA, Poland 27. OGANESSIAN Yuriy Ts., JINR, Dubna, Russia 28. OLEINIKOV Vladimir A., Institute of crystallography, Moscow, Russia 29. OMICHI Hideki, Takasaki Rad. Chem. Res. Est., Takasaki, Japan 30. ORELOVICH Oleg L., JINR, Dubna, Russia 31. ROOT David, Costar Corporation, Cambridge, USA 32. ROSTKOWSK1 Andrzej, Mil. School of Communication, Zegrze n. Warsaw, Poland 33. SAMOILOVA Lida I., JINR, Dubna, Russia 34. SCHULZ Andreas, JINR, Dubna, Russia 35. SHIRKOVA Vera V., JINR, Dubna, Russia 36. STAROSTA Wojciech, Inst, of Nucl. Chem. & Technology, Warsaw, Poland 37. TARNAWSKI Roman, Silesian Medical Academy, Zabrze, Poland 38. TWARDOWSKA Grażyna, Central Mining Institute, Katowice, Poland 39. TYS Jan, Heavy Ions Lab., Warsaw University, Poland 40. VETTER Johann, GSI, Darmstadt, Germany 41. VILENSKY Alexander I., Institute of Crystallography, Moscow, Russia 42. ZELIKSON Boris M., OPTICA JSC, Sankt Petersburg, Russia 43. ŻEMŁO Lucjan, Heavy Ions Lab., Warsaw University, Poland 44. ZIMEK Zbigniew, Inst, of Nucl. Chem. & Technology, Warsaw, Poland 45. ZHITARIUK Nikolay I., JINR, Dubna, Russia 46. ŻÓŁTOWSKI Tadeusz, Inst, of Nucl. Chem. & Technology, Warsaw, Poland 47. PASTERNAK Charles, St George's Hosp. Med. School, London University, UK