Polymer Journal, Vol. 9, No. I, pp 47-59 (1977)
Haloaldehyde Polymers. V. Polymer Blends Involving Chloral Polymers
L. s. CORLEY, P. KUBISA, and 0. VOGL
Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003 U.S.A.
(Received August 27, 1976)
ABSTRACT: Blends and interpenetrating networks of polychloral with polystyrene, poly(methyl methacrylate), and poly(methyl acrylate) as addition polymers have been successfully prepared in the forms of cylinders (plugs) or of films of 0.03-mm thickness by sequential polymerization. The addition polymers are completely extractable, but about 3096 of the polychloral is degraded during the extraction. The polystyrene extracted from the polychloral-polystyrene blends was of relatively low molecular weight. This is attributed to the high chain transfer activity of chloral for styrene polymerization in the presence of chloral. Poly(methyl methacrylate) has a comparable molecular weight, as judged by its inherent viscosity, whether the polymer has been prepared in the presence or in the absence of chloral or polychloral. In the presence of crosslinking agents, divinylbenzene for styrene, and ethylene dimethacrylate for methyl methacrylate, interpenetrating networks of polychloral were obtained; it appears that about 30% of the olefinic polymer (polystyrene) is not crosslinked and can be extracted. Poly(methyl methacrylate) is completely crosslinked. TGA was found to be a simple technique to analyze the composition of the polymer blends. KEY WORDS Polychloral / Polystyrene / Poly(methyl methacryl- ate) / Poly(methyl acrylate) / Polymer Blends / Interpenetrating Polymer Networks / Triphenylphosphine / Azobisisobutyronitrile / Thermal Degradation/ Solvent Extraction / Degradative Extraction /
Chloral homo- and copolymers with high chloral; (b) imbibing the addition monomer (which chloral content are infusible and insoluble in contains the initiator) into polychloral pieces all solvents1 and consequently cannot be blended and then polymerizing the addition monomer with other polymers by conventional melt or within the polychloral matrix; and (c) preparing solution blending techniques. a mixture of chloral, the second monomer, and Chloral polymers must be prepared by cryo a radical initiator for the olefinic monomer and tachensic polymerization, a monomer casting heating the mixture above the threshold temper technique which involves initiation above the ature. The initiator for the chloral polymeri polymerization temperature and subsequent cool zation is then added and the polymerization is ing of the mixture in order to cause polymeri carried out by sequential polymerization, where zation to a homogeneous gel. 2 Special procedures by chloral is first polymerized by cooling fol have been devised for the preparation of blends lowed by the polymerization of one (or a mixture of chloral polymers with other polymers. Three of more than one) addition monomers. basic techniques have been described3 as suc Examples of all these techniques have been cessful for the preparation of blends of chloral described in the literature. 3 For the preparation polymers with addition polymers: (a) dissolving of polymer blends by dissolving the addition the addition polymer in chloral, adding initiator polymer in chloral or in a mixture of chloral to chloral above the polymerization threshold and isocyanate, a convenient polymerization temperature, and then cooling to polymerize mixture, blends were obtained of addition
47 L. s. CORLEY, P. KUBISA, and 0. VOGL polymers with chloral polymers or copolymers. carbazole) to 11%, The preparation of these Examples have been given for "apparently homo types of blends was carried out by soaking the geneous" blends which contained ethylene/pro polychloral pieces in the addition monomer pylene rubber (4%), polystyrene (8.5%), poly which also contained a radical initiator, usually acrylates (7%), poly(methacrylate)s (7-9%), and AIBN. The polymerization of the addition poly(N-vinylcarbazole) (9%). The limitations monomer was then carried out by heating to for this polymerization technique were that (a) decompose the radical initiator. Polyisoprene the added polymer must remain soluble in the was incorporated to 16% and poly(2,3-dichloro polymerizing mixture of chloral, particularly at butadiene) to 9%. An unusual result was the end of the polymerization, and (b) the obtained with polychloroprene, which was in polymer must not interfere with the chloral corporated to 55% and gave a leathery polymer. polymerization. As a consequence, it must not This particular experiment apparently caused have active hydrogen groups or groups that some grafting of the chloroprene onto the poly would interfere in this anionic chloral polymeri chloral chains. zation. Polyblends incorporating rubbery poly Other monomers were polymerized in the mers showed a five-fold improvement in impact polychloral matrix by ionic initiators. Poly(p strength over unmodified chloral polymers. propiolactone) was incorporated to 7 % with The second technique used to prepare blends tributyl phosphine as the initiator. Poly(propy of chloral polymers with addition polymers in lene oxide) could be incorporated to 24%, poly volved preparing polychloral pieces in their final (epichlorohydrin) to 31%, and poly(2-ethylhexyl form, imbibing the polychloral pieces with an vinyl ether) to 1196, when the polychloral sample addition monomer, and then polymerizing the was soaked with the monomer and the poly addition monomer by conventional means. This merization was carried out by inserting the imbibed technique of preparing polyblends involving poly polychloral piece into an atmosphere which con chloral also has its limitations, principally the tained BF3 diethyl etherate. capacity of the chloral polymer to imbibe the In many cases of the incorporation of an addition monomer, but polyblends with as much addition polymer into the polychloral matrix, as 55% of addition monomer in the polychloral the mechanical properties of the polychloral were matrix were prepared. It has not been demon substantially altered. A typical sample of poly strated that these monomers actually swelled chloral with a flexural strength of 70 MPa and polychloral. The addition monomers filled voids an elongation of several percent had a flexural in the polychloral pieces but substantial differ modulus of 2400 MPa and an lzod impact ences in reproducibility and differences in the strength of about 0.5. The flexural strength of amounts of individual monomers incorporated the modified polymers increased from 40 to 80 into the pol ychloral matrix were not explained. 3 MPa, the Izod impact strength from 0.4 to 0.7, It is, however, clear that the monomers used the flexural modulus from 1000 to 2400 MPa, in the preparation of these blends were sub and the elongation to 15%. stantially different in polarity and reactivity. A third and potentially most versatile method One advantage of this technique was that radical, for the preparation of composites of chloral cationic, and anionic polymerization techniques polymers with addition polymers is the method could be used for the polymerization of addition of sequential polymerization. It was found monomers. earlier that this method could be most con Poly(methyl methacrylate) could be incorpo veniently carried out in the following way. rated in chloral polymers to 28%, poly(methyl Chloral and its comonomer, for example, phenyl acrylate) to 28%, poly(methacrylic acid) to 10%, isocyanate, were mixed with an addition mono poly(butyl methacrylate) to 13%, poly(2-ethyl mer and a radical initiator and the mixture was hexyl methacrylate) to 10%, and polyacrylonitrile heated above the polymerization temperature of to 18%, Aromatic vinyl polymers were also chloral. The initiator for the chloral polymeri successfully incorporated: polystyrene to 29%, zation was then added and the chloral was poly poly(a:-methylstyrene) to 6%, and poly(N-vinyl- merized by cryotachensic polymerization. After
48 Polymer J., Vol. 9, No. 1, 1977 Haloaldehyde Polymers. V.
the chloral polymerization was completed, the crosslinked polymer (the polyurethane), to pro mixture was heated to the temperature needed duce a crosslinked network within the first to activate the radical initiator and the radical polymer network. polymerization was then carried out. In our early work3 on the preparation of Conversions of chloral to polychloral of more blends of chloral polymers with addition poly than 96% have been reported in the presence mers, a number of monomers were studied for of 20% of an inert diluent, although conversions sequential polymerization, most prominently in bulk polymerizations do not exceed 85%.4 •5 styrene, methyl methacrylate, and methyl acry The use of highly volatile diluents for chloral late. It could be shown that the addition poly polymerization has been employed for the prepa mers could be extracted from the polymer blends ration of foams and sponges of chloral polymers. 6 to an extent of more than 95%. Consequently, Most addition monomers, particularly olefinic no grafting of the addition monomer to the monomers such as styrene, a-methylstyrene, and polychloral portion had occurred under these also methyl methacrylate, are inert diluents for conditions. the chloral polymerization. The limitations on It is remarkable that it was possible to initiate the use of individual monomers are the vola successfully two polymerizations in sequence by tility of the monomers and their reactivity, or two different mechanims without substantial that of the growing polymeric radical or alkoxide, interference of each of the polymerizations with with the remaining chloral monomer. The use the other. of addition monomers as "inert diluents" in The objective of this work is to prepare, by this sequential polymerization involving chloral sequential polymerization techniques, a series has the advantage that initially much higher of blends and interpenetrating networks of chlo conversions can be obtained in the chloral poly ral homopolymer with polystyrene, poly(methyl merization as compared to its bulk polymeri methacrylate), and poly(methyl acrylate). zation, and, after the addition monomer has been polymerized, a composite blend is produced EXPERIMENTAL which is more uniform and void-free than poly chloral homo- or copolymer samples of prede Materials termined final structure, such as a film or a Chloral (Montrose Chemical Co.) was dried 8 sheet. over P20 5 , distilled, and used immediately. Chloral homopolymers and copolymers with Styrene (Eastman Kodak Co.) was dried over more than 80 mo! % of chloral units are infusible calcium hydride for 24 hr and distilled under and insoluble and behave as if they were cross reduced pressure; bp 33-35°C (8 mm). linked. It was, therefore, considered possible Methyl methacrylate (MMA) (Eastman Kodak to prepare interpenetrating networks containing Co.) was dried over calcium hydride and distilled two continuous phases, the polychloral phase at atmospheric pressure; bp 100-101 °C. and the phase of a crosslinked olefinic polymer, Methyl acrylate (MA) (Aldrich Chemical Co.) by adding a crosslinking agent to the olefinic was dried over calcium hydride and distilled monomer. at atmospheric pressure; bp 80-81 °C. Interpenetrating polymer networks are com Divinylbenzene (DVB) (MC/B Manufacturing monly prepared7 by swelling a crosslinked Chemists) was dried and distilled under reduced polymer, for example, a polyurethane, with a pressure; bp 52-53°C (4 mm). Gas chroma second monomer containing a multifunctional tography showed the distillate to consist of 60-% comonomer as a crosslinking agent. A typical divinylbenzenes and 40-% vinylethylbenzene, example is an acrylate or methacrylate (with a with a trace amount of diethylbenzenes of bisacrylate or bismethacrylate as a crosslinking various isomer compositions. agent) and an initiator for the polymerization Ethylene dimethacrylate (EDMA) (Pfaltz, Bauer of the acrylic monomer. The second monomer Inc.) was dried with CaH2 and distilled under (and comonomer as crosslinking agent) are then reduced pressure; bp 85-86°C (2 mm). polymerized within the matrix of the first lightly Triphenylphosphine (Ph3P) (Aldrich Chemical
Polymer J., Vol. 9, No. 1, 1977 49 L. s. CORLEY, P. KuBISA, and 0. VOGL
Co.) was recrystallized from methanol and used mined before and after vacuum drying or solvent as a 1-M solution in benzene. extraction for each cylinder. Respective total Azobisisobutyronitrile (AIBN) (Eastman Kodak conversions for each monomer (from elemental Co.) was recrystallized from methanol and used analysis or thermogravimetric measurements on as a 0.3-M solution in benzene. the extracted cylinders) were calculated for each Benzene (Fisher Scientific Co., Certified A.C.S. sample. The "conversions" calculated for the Reagent Grade) was dried and stored over sodi individual monomers to polymers for cylinders um wire. extracted with each solvent referred strictly to Methanol, acetone, toluene, and dichloromethane the amounts of each polymer remaining in the were reagent grade solvents obtained from the sample after extraction. The amount of each Fisher Scientific Co. and were used without monomer used is considered 100%. purification. The polymer samples consisting of the blends Glass plates for the film preparation assembly of polychloral and polystyrene were first extracted were Pyrex, obtained from the SGA Scientific Co. with acetone at room temperature for 4 days. Rubber thread for the assembly was Lycra, In some cases the extraction removed as much obtained from the Globe Manufacturing Co., as 50-60% of polystyrene of low molecular Fall River, Mass. weight. In addition, absorbed chloral monomer Polymer Preparation was also extracted and the unstable polychloral A typical preparation of a blend of polychloral portion was degraded to chloral monomer. As with polystyrene by sequential polymerization is a consequence, the remaining polymer sample as follows: Into a flamed-out serum-stoppered consisted of stable polychloral and polystyrene 15 mmx 125 mm test tube were injected (with of sufficient molecular weight to be not soluble syringes) 4 ml (6.05 g, 41 mmol) of freshly dis in, or extractable by, acetone. for 24 hr at tilled chloral, 1.89 ml (1.71 g, 16.4 mmol) of The samples were then dried styrene, and 0.16 ml (0.048 mmol) of a 0.3-M room temperature at 0.02 mmHg and then ex solution of AIBN in benzene. The tube was tracted with CH2Cl2 for 4 days at room temper placed into an oil bath at 70°C. After 5 min ature (4 changes of CH2Cl2 (40 ml) for 1.5-g the tube contents had reached bath temperature. sample of polymer). The combined extracts were evaporated for 24 hr at atmospheric pres Then, 0.33 mmol of Ph3P was added as a 1-M solution in benzene and the tube was shaken sure and room temperature. The residues of to mix the reactants. The clear solution was the extracts were weighed and the conversions then rapidly transferred with a hot syringe to of addition monomers to extractable polymers a hot assembly8 to prepare a polychloral film. were calculated. The extracts (0.1-0.5 g) were The assembly was then placed into an ice then redissolved in 15-ml of dichloromethane, water bath for 16 hr. It was taken out, allowed reprecipitated from 350 ml of methanol filtered, to air dry, and placed into an oven at 70°C. and dried; and the samples were characterized by After one day the glass plates were separated their PMR spectra and by measurement of the and each polymer film was trimmed and cut solution viscosity. into two pieces. The first part was dried for The polychloral blends with linear poly(methyl 24 hr at room temperature at 0.02 mmHg. The methacrylate) and poly(methyl acrylate) were second piece was extracted with methanol (to extracted and characterized in the same manner remove unreacted monomers) in a test tube for as the polystyrene blends, except that the blends 4 days at room temperature, and dried for one with poly(methyl acrylate) were not extracted day at 0.02 mmHg. The methanol extracted with dichloromethane. film was then divided into two pieces, one of networks of polychloral which was extracted with dichloromethane to The interpenetrating remove polystyrene. with crosslinked polystyrene and crosslinked The polymer cylinder from the test tube was poly(methyl methacrylate) were prepared only similarly divided into three pieces for extraction. in film form and were extracted with refluxing Weights of the individual cylinders were deter- benzene alone.
50 Polymer J., Vol. 9, No. 1, 1977 Haloaldehyde Polymers. V.
Measurements RESULTS AND DISCUSSION Thermogravimetric measurements (TGA) were Polymer blends and interpenetrating networks performed on shavings from the extracted poly of chloral homopolymers with various olefinic mer samples with a Perkin-Elmer TGS-1 Thermo addition polymers have been prepared by a balance from ambient temperature to 430°C at sequence of two polymerizations. Initially the a heating rate of l0°C/min. For each set of mixture of chloral, the olefinic addition mono blends, it was found that the polychloral de mer, and its initiator was heated above the graded essentially completely before the addition threshold temperature of chloral polymerization. polymer began to degrade. The percentage of The initiator for chloral polymerization was total weight loss above a specified temperature then added and the chloral was polymerized by (327°C for polystyrene, 302°C for poly(methyl cryotachensic polymerization. After the chloral acrylate), and 277°C for poly(methyl methacry polymerization the mixture was warmed to the late)) could be plotted linearly as a function of decomposition temperature of the radical initiator olefinic addition polymer content of the blends for the polymerization of the olefinic addition as determined by carbon-hydrogen analysis monomer and this polymerization was then (Figure 1). carried out within the polychloral matrix. Infrared spectra of the films were recorded on a Perkin-Elmer Model 727 Infrared Spectro photometer. CCla ( CC!a PMR spectra of CDC1 3 solutions of extracted 6=0 - 1 oac --,6-0-)-I n addition polymers were recorded on a Hitachi H H Perkin-Elmer R-24 60-MHz NMR Spectrometer. Inherent viscosities of polymers extracted from CHe=C/R R·(AIBN) -(- CH2-1,-~- ( 1) the blends by solvents were determined in tolu "-Rl 50°-70°C I n ene at 30° ±0.3°C at a concentration of 0.5 g/dl Rl with a Ubbelohde Viscometer. R=H R 1=CsH5
Elemental analyses were performed by the =H =C00CH3
Microanalysis Laboratory of the University of =CHa =C00CH3 Massachusetts. In order to evaluate the successful preparation
100 of the blends and interpenetrating networks, the 0 samples were usually divided into three pieces. ]i .s One portion was held overnight at room temper b 80 ature and 0.025 mmHg to remove volatile mono mers and solvent. The second part was extracted "'> The individual samples were then analyzed for 0 -g their composition by elemental analysis, TGA, Polymer J., Vol. 9, No. 1, 1977 51 L. s. CORLEY, P. KUBISA, and 0. VOGL Table I. Composition of polychloral-polystyrene blends• Total After methanol extraction Chloral Styrene,b conversion conversiond PhaP, 0 after Total Chloral Polychloral- mol96 mol% vacuum Styre~e polystyrene after CH2Cb conversion, d t (wt%) drying, conversion, convers10n, ratio extraction, wt% % % % by weight % 0 0.2 87 68 68 100 72 17 (12. 7) 0.4 88 65 66 60 89: 11 55 28.5(22.0) 0.8 95 74 73° 79• 77: 25 64 37.5(29.8) 1.2 94 66 66 67 70: 30 52 44.5(36.2) 1.6 95 67 62• 75° 59: 41 51 50 (41.5) 2.0 93 63 58 70 54: 46 47 • Monomer cast in cylinders (plugs); 0.3-mol % AIBN with respect to olefinic addition monomer used as initiator. b Total number of moles of both monomers in mixture is 100. ° Chloral in initial monomer mixture is 100. d Conversion to polymer after extraction. • Determined by TGA; other compositions determined by elemental analysis (C, H). r Quantitative extraction of polystyrene. Table II. Composition of polychloral-poly(methyl methacrylate) blends• After methanol extraction Total Chloral MMA,b conversion conversiond 0 after Polychloral- PhaP, Total Chloral MMA after CH2Cb mo!% mo!% vacuum PMMA conversion, d conversion, conversion, (wt%) drying, ratio in extraction, wt% % % % final polymer % 0 0.2 87 68 68 100 72 17 (12) 0.4 100 98 93 100 83: 17 99 28 .5 (21) 0.8 100 88 82• 100• 67: 33 100 37. 5 (29) 1.2 100 88 77 100 63: 37 82 44.5(35) 1.6 100 94 91• 98° 63: 37 81 50 (40) 1.8 100 84 70 100 51: 49 50 a Monomer cast in cylinders (plugs); 0.3-mol % AIBN used as initiator (with respect to olefinic addition monomer). b Total numbers of both monomers in mixture is 100. ° Chloral in initial monomer mixture is 100. d Conversion of polymer after extraction. • Determined by TGA; other compositions determined by elemental analysis (C, H). tube or as transparent films when the poly extracted to an extent of more than 95%, which merization was carried out in the assembly for indicated that no grafting of the addition poly polymer film preparation. Plugs and films could mer on the polychloral was obtained. It has, be extracted with solvents for the olefinic ad however, been shown that unreacted chloral dition polymers or with nonsolvents for these acts as a chain transfer agent in the polymeri polymers. If nonsolvents were used, for example zation of the olefinic addition polymer, even methanol, only monomers and very low molec though the initiator used for these polymeri ular weight polymers were extracted. When zations, AIBN, produces radicals which are not good solvents, such as acetone, benzene, or sufficiently reactive to abstract chlorine from methylene dichloride, were used, the addition the polychloral matrix, thus causing no grafting. polymer was either completely extracted or Furthermore, the growing polymeric radicals 52 Polymer J., Vol. 9, No. 1, 1977 Haloaldehyde Polymers. v. Table III. Composition of polychloral-poly(methyl acrylate) blends• Total After methanol extraction Chloral MA,b conversion conversion• PhaP,c after Polxchloral- mol% Total Chloral MA after acetone mol% vacuum conversion,• conversion, conversion, PMA extraction, (wt%) drying, ration in % wt% % % % final product 0 0.2 88 68 68 100 72 17 (10.6) 0.4 100 83 79 100 86: 14 84 28.5(18.9) 0.8 95 64 58• 92• 73: 27 47 37. 5 (26.0) 1.2 96 57 45 90 59: 41 39 44.5(32.1) 1.6 89 50 26• 99• 36: 64 46 50 (36.9) 2.0 86 44 24 78 35: 65 32 • Monomer cast in cylinders (plugs); 0.3-mol % AIBN with respect to olefin addition monomer used as initiator. b Total number of moles of both monomers in mixture is 100. c Chloral in intial monomer mixture is 100. • Conversion to polymer after extraction. • Determined by TGA; other compositions determined by elemental analysis (C, H). Table IV. Composition of polychloral-crosslinked polystyrene interpenetrating networks• After benzene extraction Total Styrene,b conversion Polychloral- mol% AIBN,• after vacuum Total crosslinked mol% Ph3P, c mo!% (wt 96) drying, conversion, polystyrene ratio wt%• wt%• in final polymer by weight 17.5(13) 0.25 0.66 92 55 95: 5 36 (29) 0.33 0.66 94 42 84: 16 56 (47) 0.50 0.60 91 49 73: 27 • Monomer cast in films, -0.03 mm thick. b Contains 5.4-% divinylbenzene (with respect to total monomer content). c Chloral is 100. • Styrene/divinylbenzene mixture is 100. • Based on weight of film directly after polymerization, not on weight of original monomer mixture. Table V. Composition of polychloral-crosslinked poly(methyl methacrylate) interpenetrating networks• After benzene extraction Total MMA,b conversion Polychloral- Ph,P, 0 AIBN,• mol 96 after vacuum Total cross linked (wt 96) mol 96 mo!% drying, conversion, PMMA ratio wt%• wt%• in final polymer by weight 19 (14) 0.37 1.0 95 64 97: 3 39 (30) 0.50 0.9 98 60 54: 46 58 (48) 0.75 1.2 98 74 32: 68 • Monomer cast in films, 0.03 mm thick. b Contains 7.6-% ethylene dimethacrylate (EDMA) (with respect to total monomer content). c Chloral is 100. • MMA/EDMA mixture is 100. • Based on weight of film directly after polymerization, not on weight of original monomer mixture. Polymer J., Vol. 9, No. 1, 1977 53 L. s. CORLEY, P. KUBISA, and 0. VOGL produced by the addition monomers used in POLYMER BLENDS this investigation are also apparently not reactive enough to abstract the chlorine from the poly Polychloral-Polystyrene Blends chloral matrix. Blends of polychloral with polystyrene were As in other anionic cryotachensic polymeri prepared primarily in the form of 12 x 50-mm zations, polychloral is deposited as a gel from plugs in test tubes with Ph3P as initiator for the polymerization mixture; this gel appears the chloral and AIBN for the styrene poly homogeneous, but its detailed structure and mor merization. Blends were prepared of up to phology have not been investigated thoroughly. 50-mol% styrene in the monomer feed. It was However, it has chloral monomer, solvent, and, found in initial experiments that an increase in in the case of sequential polymerization, the Ph3P initiator concentration was required to addition monomer imbibed within its structure. produce satisfactory chloral polymerization with The polychloral gel, however, is insoluble and decreasing chloral concentration in the mixture. most probably this insolubility is a contributing As a consequence, as the concentration of styrene factor in its unreactivity in the subsequent radi monomer in the mixture was increased from 0 cal polymerization of the addition monomer. to 50 mol%, the amount of Ph3P used to initiate All our evidence has indicated that chloral the chloral polymerization was also increased polymerizes to a polymer which consists of a from 0.2 to 2.0 mol % . The initiator concent stable polychloral fraction, an unstable poly ration for the styrene polymerization was chloral fraction, and unreacted chloral monomer 0.3-mol% AIBN in all cases. This particular which is tightly associated with the polychloral balance, which is described specifically in Table sample. Evaporation at 0.025 mmHg at room I, was found appropriate to prepare good blends temperature overnight removed only a substantial of polychloral and polystyrene. After the poly part of the unreacted monomer. The remainder merization was completed, the polymer blends is apparently largely used up during the poly were freed of volatiles by overnight drying at merizatiou of the addition monomer as a chain 0.025 mmHg at room temperature, after which transfer agent. A substantial portion of the treatment 87-93% of polymer was left. Other chloral polymer prepared with Ph3P was unsta portions of the polymer sample were also ex ble and was degraded to chloral monomer which tracted with methanol, which is a nonsolvent was leached out by the solvent when the poly for high molecular weight polystyrene and of mer sample was extracted with methanol, acetone, course also a nonsolvent for polychloral. After or methylene chloride. In the case of methanol four days of soaking with daily changes of extraction the chloral is extracted as the hemi solvent, 65-74% of the polymer blend remained, acetal. depending on the individual blend composition. The polymerization of the olefinic addition As indicated earlier, this treatment removed monomers styrene, MMA, and MA apparently unreacted chloral if there was any left and goes to completion with AIBN, the initiator degraded unstable, most probably living but which was exclusively used for this polymeri dormant, polychloral terminated with alkoxide zation. Other radical initiators such as benzoyl end groups. The chloral conversion was 58- peroxide or other acyl peroxides or hydro 73%, as determined by carbon/hydrogen analysis peroxides were not considered because it was or, more simply and equally effectively, by de expected that they would interfere with the termination of the fraction of the blend degrading chloral polymerization. Other peroxides, such above 327°C under TGA conditions at a heating as tertiary butyl peroxide, could not be used rate of l0°C/min, which was linearly related to because their decomposition temperature was the fraction of polystyrene in the blend (Figure too high, within the range where thermal de 1). Below this temperature, polychloral degrades polymerization of polychloral, which had been essentially quantitatively to chloral monomer, formed in the first part of the sequential poly which evaporates, and polystyrene does not de merization, occurred at a significant rate. grade at all. This temperature and these con ditions have been carefully worked out in test 54 Polymer J., Vol. 9, No. I, 1977 Haloaldehyde Polymers. V. experiments, the results of which are sum our experience, a larger surface area of the marized in Figure 1. sample and better penetration of the degrading The methanol treatment left about 60-80% solvent into the sample are probably the most of the polystyrene in the polymer blend, as important factors. In a separate paper on determined by elemental analysis and/or by the perhaloaldehyde we will point out that poly TGA degration of the polymer composite. Poly chloral initiated with Ph3P exists exclusively styrene of very low molecular weight and some with polymer with low thermal stability. The small amount of styrene monomer were extracted maximum rate of degradation (MDT) of the by the methanol. The methanol solution left a polymer samples are between 120°c and 140°C, gummy residue upon evaporation. cationically prepared polymer samples have a The final compositions of the polychloral MDT of 250°C and the best stabilized poly polystyrene blends after methanol extraction chloral samples degrade at 380°C. Since poly showed that a polymer blend which was pre chloral does not swell substantially in any pared from a chloral-styrene mixture with a solvent, the size of the surface of the polymer weight fraction of 12.7% of styrene had 11% is probably primarily responsible for the vari of polystyrene in the blend. A polychloral ations of the stable fractions under apparently polystyrene blend which contained 25% of poly very similar conditions. styrene after methanol extraction was obtained Polystyrene was isolated from the polychloral from a monomer mixture with 22% of styrene polystyrene blends by an initial acetone extra in the feed. A polychloral-polystyrene blend ction, which was followed by a methylene with 30% of polystyrene was produced with an chloride extraction. Polystyrene obtained from almost similar feed ratio. As the ratio of styrene these blends by methylene chloride extraction to chloral in the monomer feed increased, the of samples previously extracted by acetone had polychloral-polystyrene blends became slightly an inherent viscosity of 0.10 dl/g, indicating richer in polystyrene. This seems to indicate very low molecular weight. If the same sample that the polymerization of chloral is somewhat of styrene was polymerized with the same decreased at high styrene concentration or that amount of AIBN initiator in bulk, polystyrene the proportion of unstable polychloral in the was obtained with an inherent viscosity of total increases as the polychloral-polystyrene 0.94 dl/g. This indicated that the growing blend increases in polystyrene composition. This polystyrene radicals most likely had undergone is also borne out by the observation that although extensive chain transfer with chloral. This is total conversion after vacuum drying remains particularly important since it would have been relatively constant with increasing styrene/chloral expected that the polymerization of styrene in ratio, the total percentage of chloral conversion a rigid matrix might have been subject to the to polychloral after methanol extraction decreases Trommsdorff effect, which would have caused slightly. an increase in molecular weight. The molecular If one compares the observed apparent con weight of polystyrene extracted from the poly version of chloral after methylene chloride ex chloral-polystyrene blends was significantly less traction with the styrene content of the monomer than that of the polystyrene obtained under feed, one finds that the percentage of stable bulk polymerization conditions; this indicates polychloral decreased as the styrene content extensive chain transfer, which is expected increased in the original monomer mixture from from the polystyrene radical with chloral. 72% for no styrene to 47% for 41.5-wt % styrene. Polystyrene extracted from the polychloral There could be three reasons for this result: polystyrene blends was also investigated by a higher fraction of dormant living polychloral, PMR spectroscopy and compared with bulk a greater surface area of polychloral in the polymerized polystyrene. The PMR spectra of blend which is exposed during extraction, or the two samples were found to be superim lower molecular weight polychloral. We expect posable. that all three contributions play a role in the Elemental analysis of polystyrene prepared in instability of such polychloral samples, but in the presence of chloral by sequential polymeri- Polymer J., Vol. 9, No. 1, 1977 55 L. s. CORLEY, P. KUBISA, and 0. VOGL zation showed 0. 78 % of chlorine, indicating a lindrical pieces were divided into three parts. number-average molecular weight of 13,000 or The first portion was evacuated overnight at a DP of about 100 if one assumes 3 Cl atoms 0.025 mmHg; it was found that no weight loss per polymer molecule, a result which is in occurred, indicating that the polymerization had agreement with the chain transfer activity of gone to completion or that the small amount the chloral in styrene polymerization. The poly of chloral which may have been left over after styrene samples on which the viscosity measure the polymerization remained absorbed in the ments and chlorine analyses were performed polymer sample. The second portion of the had been obtained by methylene chloride ex polymer was extracted with methanol to remove traction from blends which had previously been monomers and low molecular weight materials extracted with acetone, which had removed and at the same time to degrade unstable poly about 65% of the polystyrene. Hence the aver chloral portions. The third portion was ex age molecular weight of the total polystyrene tracted with acetone for this same purpose and produced in this system was undoubtedly lower. then divided into two sections, one of which The low molecular weight of polystyrene pro was then extracted with methylene chloride to duced in the sequential polymerization of poly remove high molecular weight PMMA. Acetone chloral and polystyrene is probably the major was found to be ineffective in extracting the reason for the difference in observed styrene high molecular weight polymer. conversions as determined after methanol and The total conversion after exhaustive methanol acetone extraction. Much of the polystyrene extraction was between 85% and nearly 100%. produced is of sufficiently low molecular weight This is substantially higher than the 60-70% to be even soluble in, and consequently extracted which was observed for the polychloral-poly by, methanol. styrene blends. The fact that the conversion Polystyrene was quantitatively extracted by of MMA to PMMA is almost uniformly 100% methylene chloride from the blends, as shown seems to indicate that all the weight loss that by the absence of any of the characteristic is observed during the extraction comes from polystyrene bands in the infrared spectra of the degradation of an unstable fraction of poly polychloral-polystyrene blends extracted with chloral which is, however, much less in amount methylene chloride. than in the case of blends prepared from chloral Several of the blend cylinders after extraction and styrene. These results indicate that the with acetone were almost transparent, similar MMA and/or PMMA play an additional bene to copolymers of chloral with isocyanates and ficial role for the stabilization of the polymer in sharp contrast to unmodified chloral homo of the chloral portion of the blend and possibly polymer which is nearly opaque. This effect act as acylating agents of living or dormant was particularly pronounced with the plugs · polychloral chains. This would explain a higher which contained 10 to 20 wt% of polystyrene percentage of stable polychloral after extraction after acetone extraction. Methanol extracted the presence of a small amount of carbonyl blends did not show this transparency. absorption in polychloral after extraction, and Polychloral-Poly(methyl methacrylate) Blends also the fact that only 95% of PMMA can be Blends of polychloral and PMMA were made extracted. If alkylation of anionic living poly which contained up to 40 wt% (up to 50 mol %) chloral with PMMA occurred this would mean the of MMA in the original monomer mixture. formation of a small amount of PMMA with a The chloral was initially polymerized by cryo polychloral long branch, linked through the ester tachensic polymerization with 0.2-2.0-mol % group. A similar termination reaction has been Ph3P as the initiator. As with the chloral observed earlier with acid chlorides in anionic styrene mixtures, the amount of initiator had chloral polymerization but not yet with esters.9 to be increased as the percentage of MMA in The ratio of polychloral to PMMA in the the monomer mixture was increased. final polymer is very similar to the initial feed After the sequential polymerization to prepare ratio of chloral and MMA. However, at high the blends was completed, the 12 x 50-mm cy- percentages of MMA the polychloral fraction 56 Polymer J., Vol. 9, No. 1, 1977 Haloaldehyde Polymers. V. in the blend is less because of the formation in the monomer feed. The relatively high value of a higher percentage of an unstable fraction of MA conversion to PMA combined with a of polychloral which is degraded during the low chloral conversion value gave a final blend extraction. mixture consisting of 2 parts of PMA to 1 part PMMA, when extracted from the blends with of polychloral at 50-mol % MA in the feed. methylene chloride, showed an inherent viscosity In polychloral-PMA blends the extracted of 0.48 dl/g, which is comparable to the inherent stable blends are enriched in PMA over the viscosity (0.31 dl/g) of PMMA obtained with the initial monomer feed ratios and indicate that same monomer, initiator concentration, and an unusually large proportion of the polychloral polymerization temperature in bulk. The ex portion of the blend is degraded during the tracted sample of PMMA was compared with methanol extraction. We have no plausible the bulk-polymerized sample by PMR. The explanation at this time why a much larger spectra of the two samples were found to be fraction of the chloral polymer portion is un superimposable. stable (76% vs. 32% in the standard) when the PMMA was extracted to more than 95% from chloral polymerization with Ph3P is carried out the blends by methylene chloride (Table II) as in the presence of large amounts of MA. A shown by the carbon/hydrogen analysis of a larger amount of Ph3P initiator had always been sample containing 49 wt% PMMA before ex used for the chloral polymerization at the higher traction. Likewise, films of polychloral-PMMA concentrations of olefinic monomers used for blends continued to show definite, though not the blends, but no such pronounced decrease strong, PMMA carbonyl bands after methylene of the stable fraction had been detected in blends chloride extraction. It is believed that the lack of polychloral-polystyrene and polychloral of total extractability of PMMA is due simply PMMA at higher concentrations of Ph3P and to impaired diffusion of high molecular weight olefinic addition monomer. PMMA through the polychloral matrix. It is The acetone extracted samples of high PMA not believed that grafting occurred, in part polychloral ratio also show substantially decreas because extracted PMMA gave a negative ed conversion of chloral to polychloral, which Beilstein test for chlorine and no chlorine was can only mean that this is an inherent property detected by elemental analysis. of the sample, not of the extraction method. PMA extracted from the blends of polychloral Polychloral-Poly(methyl acrylate) (P MA) Blends and PMA had an inherent viscosity of 0.31 dl/g, Blends of polychloral and PMA were also in comparison with an inherent viscosity of prepared under conditions similar to those de 0.89 dl/g for PMA prepared in bulk with the veloped for the preparation of polychloral same monomer, initiator concentration, and PMMA blends (Table III). The combined polymerization temperature as for the blend monomer conversion to polymer blend after polymerization. It could be that in the bulk vacuum drying was always greater than 85%, polymerization, branching occurred with a sub indicating high conversions of both monomers sequently higher viscosity-average molecular to polymer. The total conversion to polymer weight in the resultant polymer, which is not blend after methanol extraction decreased as the possible in the case of the MMA polymerization, mole percent MA in the monomer feed mixture this fact. increased. The percent conversion of MA to but we have not attempted to establish methanol-insoluble PMA dropped from nearly Some chain transfer with chloral monomer quantitative in the 17-mol % mixture to 78% does occur in the radical polymerization of MA in the mixture containing 50-mol % MA. The in the polychloral matrix, because acetone-ex chloral conversion to methanol-stable polychloral tracted PMA showed a chlorine content of decreased from 79% at 17 mo! % to 24% at 0.69% by elemental analysis. With the assump 50-mol % MA in the initial monomer mixture. tion of 3 Cl atoms per polymer molecule, this These values are also reflected in the drop result indicates a number-average molecular of the total conversion after methanol extraction weight of 15,000, corresponding to a DP of from 8396 to 44% witn increasing MA fraction about 180. This chain transfer in MA polymeri- Polymer J., Vol. 9, No. 1, 1977 57 L. s. CORLEY, P. KUBISA, and 0. VOGL zation is not as effective as in styrene polymeri overnight at room temperature at 0.025 mmHg zation but more effective than in MMA poly was more than 95%. Extraction for 48 hr with merization, which showed no incorporation of refluxing benzene removed 25-40% of the poly chlorine into PMMA and whose average molec mer. The relatively low conversion to polymer ular weight was also not decreased when the after benzene extraction, as compared to the polymerization was carried out in sequence after methanol extraction of noncrosslinked PMMA chloral polymerization. in polychloral (Table II), indicates that the 20% Polychloral-Crosslinked Polystyrene Interpenetrat difference in the extracted total yield of the polymers is probably caused by degrative extrac ing Networks tion of polychloral which seems to occur more Sequential polymerization of chloral and effectively with benzene but not with methanol. styrene was also carried out in the presence of Poly(methyl methacrylate) in the IPN seems to 5.4% of divinylbenzene to crosslink polystyrene be completely crosslinked at medium or high and to form an interpenetrating network of concentrations of MMA but not at low concen polychloral with crosslinked polystyrene (Table trations of MMA. In IPN's from chloral and IV). As can be seen, the total conversion of MMA, crosslinked with EDMA, the polychloral monomers to polymers is higher than 90% after part still has a very substantial unstable fraction, vacuum drying at 0.025 mmHg. which is most noticeable in IPN's with high The second part of the polymer sample was MMA (and EDMA) content. then extracted for 48 hr with refluxing benzene. Further work on the preparation of polymer The benzene extracted unreacted monomers blends and IPN's based on chloral homo- and (chloral, styrene, and divinylbenzene) and also copolymers with olefinic addition polymers will the unstable portion of polychloral and extracted be necessary to describe in greater detail the a noncrosslinked portion of polystyrene. In a chemical composition, morphological structure, separate experiment it was shown by IR spectro and physical and mechanical structures of these scopy that the extraction with refluxing benzene polymer composites. These characterizations was effective in removing the noncrosslinked are very important because the reproducibility polystyrene from the polychloral matrix. of these preparations depends on many factors As shown in Table IV, the total conversion which have to be observed very carefully. of the monomer mixture to the JPN was re latively low, though highest for low percentages Acknowledgements. This work was supported of styrene in the monomer feed. It is known by the National Science Foundation and the that as much as 10% of unreacted chloral Materials Research Laboratory of the University monomer and 20-25% of unstable polychloral of Massachusetts. One of us (P. K.) was on a may be present in the portion of the polymeri leave of absence from the Centre of Molecular zation mixture that comes from the chloral part and Macromolecular Studies in Lodz, Poland, of the monomer feed which is degraded and to work at the University of Massachusetts. extracted by benzene. In general, half of the We would also like to express our thanks to polystyrene that is produced in the polychloral the Montrose Chemical Company, particularly matrix is crosslinked and the other half can be Mr. H.J. Wurzer, for their generous supply of extracted by benzene. chloral. Polychloral-Crosslinked Poly(methyl methacry late) Interpenetrating Networks REFERENCES Interpenetrating networks of polychloral and I. 0. Vogl, H. C. Miller, and W. H. Sharkey, PMMA crosslinked with 7 .6-wt % ethylene di- Macromolecules, 5, 658 (1972). methacrylate (EDMA) were prepared as films 2. 0. Vogl, U.S. Patent 3 454 527 (1969). about 0.03-mm thick by sequential polymeri 3. 0. Vogl, U.S. Patent 3 707 524 (1972). zation with 0.4-0.8 mol % of Ph3P as the initi 4. K. Hatada, L. S. Corley, Sh. S. Vezirov, and 0. ator for the MMA polymerization. Vogl, Vysokomol. Soedin., in press. The total conversion to polymers after drying 5. 0. 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