PERU
RADIATION POLYMERIZATION OF VINYLENE CARBONATE
by
Norman G. Schnautz Anne Lustig Henriette Roesch
ATOMIC ENERGY BOARD Pelindaba 9 PRETORIA May 1978 Republic of South Africa PER-11-1
ATOMIC ENERGY BOARD
RADIATION POLYMERIZATION OF VINYLENE CARBONATE
by
Norman G. Schnautz,* Anne Lustigand Henriette Roesch
"Chemistry Division Postal Address: Private Bag X256 Pretoria 0001
May 1978 ISBN 0 86960 655 7 »•**•**! »•#•
CONTENTS
P.igu
SAMEVATTING 3
ABSTRACT 3
1. INTRODUCTION 4
2. EXPERIMENTAL 4
2.1 Materials 4 2.2 Irradiation Sources 4 2.3 Sample Preparation 4 2.4 Analyses 4 3. RADIATION-INDUCED HOMOPOLYMERIZATION OF VINYLENE CARBONATE ... 4
3.'! Introduction 4 3.2 Results and Discussion 4
4. RADIATION INDUCED COPOLYMERIZATION OF VINYLENE CARBONATE WITH ISOBUTYL VINYL ETHER 6
4.1 Introduction 6 4.2 Results and Discussion 7
5. RADIATION INDUCED TELOMERIZATION OF VINYLENE CARBONATE WITH CARBON TETRACHLORIDE g
5.1 Introduction g 5.2 Telomerizp'.on Kinetics g 5.3 Results e id Discussion 11
6. ACKNOWLEDGEMENTS ,7
7. REFERENCES PER 11 3 SAMEVATTING ABSTRACT
Die stralinijSgeinclusetircle polimenserin.j van The radiation-induced polymerization of vinylene viniieenkarbonaat met n suiwerneid «an 99.97 °o is carbonate of 99,97 % purity has been investigated. The ondersoek. Die verband tussen omsettings- en bestralingstyd relationship between conversion and irradiation time is is streng lineêr, selfs by die laagste omsettings, wat dus strictly linear, even at the lowest conversions, thus proving bewys dat die normale induksietydperk wat vir die that the normal induction period observed for the pclimerisemg van vinileenkarbonaat met laer suiwerheid in polymerization o' lower-purity vinylene carbonate indeed ag geneem word inderdaad die gevolg van die aanwesigheid results from the presence of an inhibitor. Although the van 'n stremstof is. Hca/vel die stremstof me uitgeken kon identity of the inhibitor has not been established, it has word nie, is daar getoon dat dit nie been shown that it is not dichlorovinylene carbciate. An dichloro-vinileenkarbonaat was nie. 'n Aktiveringsenergie activation energy of 15,1 kj/mole was calculated for the van 15,1 kJ/mol is vir die bomopolimeriseerproses bereken. homopolymerization process. Die stralingsgeihduseerde kopolimerisering van vinileenkarbonaat [M]) met isobutielvinieleter (M2) is oor The radiation-induced copolymerization of vinylene die temperatuurstrek van 40 tot 80 °C ondersoek. Die carbonate (Mi) with isobutyl vinyl ether (M2) has been monomeer se reaktiwiteitsverhoudings r-j en r2 is investigated over the temperature range o' 40-80 °C. The onderskeidelik as 0,118 en 0,148 vasgestel, en n monomer reactivity ratios ry and r2 werj determined to be aktiveringsenergie van 31,8kJ/mol is vir die 0,118 and 0,148 respectively, and an activation energy of kopol'meerproses bereken. 31,8 kJ/mole was calculated for the copolymerization Die stralingsgeihduseerde tclomerisering van process. vinileenkarbonaat met koolstoftetrachioried is oor 'n konsentrasieverhoudingstrek van 4 tot 20 vir telogeen tot The radiation-induced telomerization of vinylene monomeer ondersoek. Daar is gevind dat die carbonate with carbon tetrachloride has been investigated vormingstempo van die adduk nr~1 ona'hanklik van over a telogen to monomer concentration ratio range of 4 monomeerkonsentrasie an regstreeks in verhoudi.ig tot die to 20. The rate of formation of the n=1 adduct was found telogeenkonsentrasie was, met 'n kragafhanklikheid van die to be independent of monomer concentration, directly orde 0,38 van die stralingsintensiteit, war oor die algemeen proportional to the te'ogen concentration, and exhibiting a met die afgele de temp'overgelykings oorei-ngestem het. 0,38 order power dependence on the radiation intensity, in Daar is verder gevintl dat die vormingstempc van die general agreement with the derived rate equations. The rate telomeer n 2 onafhanklik van beide monomeei en of formation of the n~ 2 telomer was found to be telogeenkonsentrasies en van stralingsintensiteit was wat nie independent of both monomer and telogen concentrations in ooreenstemming met die afgeleide tempovergelykings and radiation intensity, which is not in agreement with the was nie. Die eerste en tweedí kettingoordragkoëffisiente C-\ derived rate equations. The first and second chain-transfer en C2 is onderskeidelik as 0,116 en 0,34 bepaal, en die coefficients C1 and C2 were determined to be 0,116 and aktivenngsenergiee vir d.n vorming van die adduk n 1 en 0,34 respectively, and the activation energies for the die telomeer n 2 is onderskeidelik 05 17,6 en 64,9 kJ/mol formation of the n-1 adduct and nr2 telomer were bereken. calculated to be 17,6 and 64,9 kJ/mole respectively. PER 11 4 1. INTRODUCTION 24 Analyses
Newman and Addor described both the first synthesis Tha homo and copolymers which were formed were and polymerization of vinylene carbonate (VCA) (1.2|. transfered to preweighed vials with the aid of 5 ml of 50 % dimethylfurmamiae-acetone solution and dried in vacuo at 50 °C to a constant mass. Telomers which were formed were transferred to vials with the aid ot 5 ml of acetone and subjected to GC analysis. VGA is interesting as a vinyl monomer for radical Gaschromatographic analyses werr carried out on a polymerization processes in that, although its overall rate of Perkin-E'mer 900 gas chromatograph. Monomer purity was polymerization is low compared with methyl methacrylate, determined using a 1/8 inch diameter stainless steel column it is unusually high tor a vinyl monomer in which the vinyl 2 m long, packed with a mixture of 10% FFAP on group is symetricaily disubsiituted. Polyvinylene carbonate Chromosorb W AW-DMCS. Analysis of telomer-acetone (PVCAi is of interest because it can yield a tough, clear solutions was carried out using a 1/8 inch diamete stainless plastic from which both films and fibres have been stsel column 2 m long, packed with a mixture of 5 % Dow produced (3|. Comprehensive reviews of the preparation Corning silicone high-vacuum grease on Chromosorb G and polymerization of VCA have been reported by Field AWDMCS. and Schaefgen [3], and Hardy (4|. Mass spectra were determined using a GC-MS system consisting of a Varian Aerograph Series 1200 gas This report will be concerned with three aspects of chromatograph coupled to a Varian Mat (Gmbh) CH7 mass the gamma-radiation-induced polymerization of VCA. The spectrometer. first is a study of the reaction kinetics of homopolymerization of VCA, and the second, the Infrared analyses were carried out on a Perkin-Eimer copolymerization of VCA with sooutyl vinyl ether (IBVE). 237 grating infrared spectrometer. Polymer films were cast The third aspect is an investigation of the telomerization of on potassium bromide discs. VCA with carbon tetrachloride. Number average molecular masses were obtained by membrane osmometry, acetone being used as the solvent 2. EXPERIMENTAL for the copolymers at 30 °C. Thermal analyses of the copolymers were carried ojt 2.1 Materials on a Perkin-Elmer DSC 18 differential scanning calorimeter.
Vinyiene cartonate was prepared by the method of 3. RADIATION-INDUCED Newman and Addor [ 1) and modified as suggested by Zief HOMOPOLYMERIZATION OF VINYLENE and Schramm |5|. Purification was by vacuum distillation CARBONATE over sodium borohydride, a; described by Field and Schaefgen |3). The purity of the resulting product as 3.1 Introduction determined by GC ranged from 99,5 % to 99,57 % after repeated fractional distillations. Dichlorovinylene carbonate Newman and Addor first reported the polymerization (DCVCA) was prepared by the method of Scharf, Pinske, of VCA in 1955 |2j. Since then numerous authors have Feilen and Drcste |6). Isobutyl vinyl ether (Fluka AF) was reported their findings concerning both fundamental and vacuum-distilled prior to usage. Carbon tetrachloride and all practical aspects of the polymerization r,' 'A. solvents were of analytical grade. To date, studies on the polymen/ ,i of VCA have been coif;ned primarily to chemical-initiated free-'adical 2.2 Irradiation Sources processes. There are only a few reports in the literature concerning the radiation-induced liquid-state and solid-state polymerization of VCA [7,8|, and Krebs and Schneider Irradiations were carried out in both an AECL have reported in detail on the a[ parent induction period in Gammabearn 650 (50 kCi) and a Gammaceli 220 (10 kCi) thp initial stage of the radiation-indu:ed polymerization of irradiation source. Dose rates for both sources were VCA |9,10). The purpose of this particular aspect of the determined by Fricke dosimetry. Irradiations at different radiation polymerization of VCA is to explain this unusual temperatures were carried cut in both source;, using a induction period, which normally exhibits itself at metal sample container thiough which an appropriate conveisions below 10% as an acceleration of the rate of cooling or heating fluid could be passed. Temperature polymerization. control over the range 30 °C to 90 °C, to an accuracy of •0,2 °C, was obtained using a cryostat. 3.2 Results and Discussion 2.3 Sample Preparation The polymerization of VCA of 99,5% purity (GC) Monomer, comonorrer, and monomer-teloge.i was carried out initially at a temperature of 65 °C and at a mixtures were prepared by weighing the appropriate dose rate of 3,0 kGy/h. The chlorine content of this VCA quantities of monomers and telogen into 3-ml giass sample was 0,25 % The rate curve shown in Figure 1 ampoules at room temperature, subjecting each sample to Clearly illustrates the relationship between percentage four consecutive degassing eye'es and sealing under vacuum. conversion and irradiation timo The above VCA sample reaii 5
>•''.'A i'.)9.l>' : an;i 0,iL c CD in dimethyl sulfoxide a) Y.\)) vvjs pit;: and and Irradiated at 65 °C and at a dose 'ji.i of '!0 kGy/h. A: C3n be seen in Figure 2, a strictly p.-: ÍV" ,i ••a- relationship exists between converson and irradiation tt", it t lime v.n at the iovust conversions, although the rate of poivieiization is the same as the linear region [i.e. > 10 u) for tht bulk polynx-ii/ution process Furtre, rioie, if the urn j' rate of polymerization obtained foi solution PM ni.>r;zation of VGA is a result of diluting the gel effect •;,; pr.iii'insnt in hulk polv mentation, then much lower o;. osit!e> should be obseived for solution polymerization or VCA. As can he seen in Figure 3, there is a drastic !>-.Kj;vnrial ntcreav in solution viscosity for bulk pjiyrnerlzation ot VGA as total conversion approaches 4 %, uii.ndS in the 20 % DMSO solution only a gradual increase in solution viscosity is observed. This obse'va;ion wouid appear to be in agmement with the first explanation, i.e. liiiusuji gel effect
i, d , ,i i i, .( ,1 (i .i .. .pi i -.!'. • •.!•.:•
II.Mile. '.M ; ,•:: ii M :'• i " : r > ; '
,, suit , : . i;1 j' ; ..'. . ' ; '
,d,) . ,i I' I' •• ' •:•' .'••.,
,> i.,'.'... , I " ; ' :
,i i e-. , :,' . • .
,/,). n .' I '. .,\ I . |. : i ,/',,'j,.J/.'/u', ', .' • ,', M//M,/ .ft I !;1: '•./.!' í ../'/ ,'7,n'e
: :J .•ISi.l-u I . . • i j I" . : • I'll-.,' il II.• /// Ji,>. 1... ' S,//7,;\'I/L'^Í f) , I.
I.i i )i r.j |e*>i. • .I'M '• ii.r.1' - ', : I ' nil.i at ii t/o,e >jtr ot3,0 !<(. .v II.
•>'..•;.,!! r ill. ,)' ,., '. •:.:,,• ,, ,,
til.' ,", :,i • i, .,. )i :. ,.'.•'
! .n kT .vii r.;su!t n. ..i .' . , ..... ,, po'yilie'i/ in ; . The Amu. .. pi,,.: .1: :. ' ,-• ' f : :',••,
that th • i 'tia, lllilJ.ri' p.i'iii ,, -i ij • ii i ,u ,; .,ie or, ,,;i:, ' i.t .in iiiiiih.toi i'. I:.-; r!ii: I >\
Sclit. iik, : ^ us , ', u,,, 'in i I!,! !:,. ,i! ,i ; . i .ri
r IS dicllioir ill.li r ,. Crt, b'V .ti (I.CJl.'.-'l | /| i<|i,)|, ! / lie
iiihiDitiiiii effect ol IJC i A ,, v.r. ;'-n!ci ai.u Ii II
1 0,'j „ UI-'.'C»" i.oiripl•:!• e, - .ppii \" i i Imli , : ,c..i I 1 5 polyn.e'i/aii ... ,1 '•.'"-'- | j|
In l-'t d, IIIKIJI : s.il , ;. i ,i ... Hi/. 1 ., ,p|<0. '. iti i: f I 11 e .piH ; ,<1| .' ; : , il Mi/iiu/iii'i pnh'mcr solution i /s< •%/'/>• f Ol • ,;ri, ii.. ,i ,- • i, . 11 t /> i/ ///'/(lion nl /)i-/'i aittigv com vision
IO;> .. :, • :i ,. ii , ,• , .... , . . ! ' . ,
,11 ' 11'. •:. ill I ,,'.;,,', i , i . While the above ohs. ivations lend support lu the idea i c ; unusual gel eflect, Ihey do not Const iute proof. Thus tin •i-epciratiun of VGA tree ,)f chlorine contamination was nUampUnl To this unci 1)9,9 % pure W(.A .vn» suhtectnl to
: I. Ml.'I i repeated ttactional distillation using an efficient packed r,.,lu,-nn at a influx iatio of ?0 (return) to 1. Tlie middle PER 11 6 fractions were collected and subjected to repeated fractionation until a middle fraction purity of 99.97% (GO was achieved. The chlorine content of th's sample was zero per cent. Polymerization at 65 °C and at a dose rate of 3.0 kGy/h afforded a completely linear relationship between conversion and irradiation time, as is shown in Figure 4, even at the lowest conversions. This is conclusive proof that the initial induction period observed for polymerization of lower-purity VCA indeed results from the presence of an inhibitor and does not stem from an unusual gel effect.
Fig. 5. Gas chromatogram of'99,5% pure vinylene carbonate.
The influence of temperature on the radiation-induced polymerization of VCA was also investigated. From the Arrhenius plot in Figure 6, an overall activation energy of 15,1 kJ/mole was calculated. In the case of chemical-initiated polymerization of VCA using Fig. 4. AIBN (azobisisobutyronitrile), Smets and Hay ash i found Bulk-phase polymerization of vinylene carbonate the overall activation energy to be 92,9kJ/mote [12]. at 65 °C and at a dose rate of 3,0 kGy/h. Hardy et al have found the activation energy for the ratio Monomer purity was 99,97% and chlorine content 0 %. kpk^ to be 31,0 kJ/mole [13]. Since in a radiation-induced polymerization process the activation energy of the initiation step is essentially zero, the value of the overall activation energy should be dictated solely by the In order to ascertain the identity of the responsible activation energy for the ratio kpkf'/a. If Hardy's value of contaminant or contaminants, a 99,5 % pure sample of 31.0 kJ/mole is to be taken at face value, and there is no VCA was subjected to detailed GC analysis. In all there reason why it should not be, then our own valua of were over fifteen low-level irr purities, all of lower boiling point than VCA. A typical gas chromatogram is shown in 15.1 kJ/mole would appear to be somewhat low. However Figure 5 and the major impurities are marked from 1 th:„ lower value could result from the extreme purity of the through 7. Clearly the predominant impurity is number 3. monomer used and may thus represent the more realistic GC analysis of an authentic sample of DCVCA showed that value. it exhibited a retention time identical to that of impurity 3. 4. RADIATION-INDUCED However, GC-MS analysis of the above VCA sample showed COPOLYMERIZATION OF ViNYLENE conclusively that impurity 3 was a nonchlorine-containing CARBONATE WITH ISOBUTYL VINYL ETHER hydrocarbon with a molecular mass of 130, thus clearly eliminating DCVCA as a possible impurity. The 4.1 Introduction identification of impurity 3 from its mass spectrum has not been possible. One possibility would be ethyl acetoacetate The radical copolymerization of VCA was first (molecular mass 130) obtained by triethylamine-catalyzed reported by Price and Padbury, who copolymerized VCA condensation of ethyl acetate. However, an authentic with comonomers such as vinyl acetate, methyl vinyl sample of ethyl acetoacetate exhibits a different retention ketone, isoprene, chloroprene, acrylonitrile, and esters of time than does impurity 3. Unfortunately the acrylic acid [14]. The chemical-initiated free-radical concentration of the remaining impurities is far too low to copolymerization of VCA with isobutyl vinyl ether (IBVE) yield mass spectra capable of interpretation. A GC has been reported in detail by Schulz and Wolf [15], who chromatogram of a 99,97 % pure VCA sample showed that determined the monomer reactivity ratios to be the only significant remaining impurities were numbers 6 ri(VCA) = 0,160 and r2(IBVE) = 0,185. and 7. Based on an interpretation of the mass spectra of To date, studies on the copolymerization of VCA impurities 6 and 7, impurity 6 might be have been limited primarily to chemical-initiated chlorine-containing. free-radical processes. Although Schulz and Vollkommer PER 11-7 have studied tht radiation mductd copoi/meiization of to VCA with IBVE in a variftv of solvent systems |16|, the influence u! monornei composition and ir radiation 09 temperature on the rate ot co polymerization for the VCA-IBVE system has not been repotted. 08 07
06 4 O ^»- • u.> 05l-
04 -
03
Q2
0.1
01 02 03 04 05 06 07 08 Q9 10 *VCA
Fig. 7. Comparison of the copolymer as a function of the mole fraction of vinylene carbonate in the comoncmer mixture at 50 °C and at a Jose rate of.?, 6 k(iv 'h. / /./. 6. Kah
35 4.2 Results and Discussion
The copolymerizat'un of VCA (Mi) with IBv/E: (M2) was ca'rieii out at an irradiation temperature of 50 °C and H at a dose rate of 3,6 kGy/h, ana the mole fraction of VCA was varied fiom 0,1 to 1,0. The copolymenzation curve thus obtained is shown in Figure 7, whue the copolymer in terms of VCA is expressed as a function of thecomonomer 3 2 5 SI composition. The monome' ruactivity ratios r> and <2 were calculated by the Fineman-Ross method |17| and values * r obtained were 0,118 and 0,148 respectively. This agrees very closely with the values of 0,160 and 0,185 obtained by 20 Schulz and Wolf for the chemical (AIBN) initiated • • copolymerization of VCA with IBVE [15|. This result is as would be expected, because the monomer reactiv.ty rat.os t\ and r2 are determined solely by the rates of propagation 15 of the growing polymer chains, which themselves are independent of the nature of the iritiation step. The rate of copolymerization was also determined as a function of monomer composition. At conversions below 01 02 03 04 05 00 07 08 09 10 10 % there is an acceleration of the rate of *VCA copolymenzation, and thus the rate data were treated by means of a polynomial recession technique. The tig. 8. relationship between the rate of cc polyrneiization and Plots of ( ) rate of copolymeri/ation monomei composition lor a conversion of 4 "0 is shown in and (*') nurnbtr-average molecular mass Fiqne 8 Thf maximum iate of cnpolymenzation occurs of the copolymer as a function of when the mole fraction of VCA in the monomei solution is the mole fraction of vinylene carbonate 0,7. Untlei these t.onditiuns the mole fraction of VCA in in the comonomer mixture at 50 (>C the poi /!'!<•' ir. product i.. app'o„irn.it*.'!.- n h? and at a dose rate of 3,6 kCiy/h. PERU 8 That the polymeric product thus obtained is a true being called a "taxogen", n being any integer greater copolymer cannot be ascertained by a comparison of the than or.3, X and Y being fragments of the telogen infrared spectra of the polymeric product and respective attached to the terminal taxogens. homopolymers. The infrared spectrum of the polymeric product contains only the absorption bands characteristic 10' for both the individual homopolymers. However, thermal analysis of the polymeric product indicated a sharp decomposition at 315 °C. This is in contrast to poly(VCA), which exhibits a decomposition point at 245 °C. A 50 % mixture of poly(VCA) and poly(IBVE) also exhibits a sharp 245 °C decomposition point. From this information and from the copolymerization curve in Figure 7, it can be concluded that when the mole fraction of VCA in the monomer solution is of the order of 0,5 to 0,7, a completely alternating copolymer is formed. The molecular mass of the VCA-IBVE copolymer was E = 31,8 kJ/mol* determined as a function of the monomer composition at a conversion of 4 %. The number-average molecular mass Mn is normally expected to be at a maximum at the same 10 composition at which the rate of polymerization is at a maximum, Ir this case, Mn appears to be at a maximum where the mole fraction of VCA in the monomer solution is 0,4. However, the copolymerization of VCA and IBVE is complicated by the fact that the copolymer is extremely insoluble in IBVE solutions and precipitates from solution when the mole fraction of VCA in the monomer solution is less than 0.9. From the Arrhenius plot in Figure 9, an activation energy for the radiation-induced copolymerization of VCA with IBVE of 31,8 kJ/mole was calculated. An activation energy for this system has not been previously reported. By way of comparison, the overall activation energy for the 2.7 2.8 29 3.0 ai 3T2 homopolymerization of VCA, initiated chemically by 3 AIBN, has been reported to be 92,9 kJ/mofe [12], and 10 31,0 kJ/mole for the ratio kpk't'7' [13]. Because the T Fig. 9. activation energy for the initial step of a radiation-induced Rate of copolymerization as a function vinyl free-radical polymerization process is normally zero, of the irradiation temperature at a mole fraction the latter value of 31,0 kJ/mole is in good agreement with the value of 31,8 kJ/mole for the radiation-induced process. ofO, 70 for vinylene carbonate in the comonomer mixture at a dose rate of 3,6 kGy/h. 5. RADIATION INDUCED TELOMERIZATION To date no general criteria have been extablished to OF VINYLENE CARBONATE WITH CARBON distinguish between telomers and polymers. Since TETRACHLORIDE chain-transfer agents are often added in polymerization to control molecular mass, a distinction resting solely upon 5.1 Introduction the presence of chain-transfer agents would be misleading. Arbitrarily, products having molecular masses less than As early as 1945 Kharasch, Jensen and Urry had 5 000 are often considered telomers. Sometimes the term reported the free-radical addition of carbon tetrabromide oligomerization is used in place of telomerization, but here across an olefins double bond, and that adducts containing oligomer refers to a low molecular-mass product which does two or more molecules of the olefin to one molecule of not necessarily incorporate the elements of a chain-transfer carbon tetrabromide could be obtained [18]. However, it agent into its structure. For the purpose of this report the was not until 1948 that Hanford and Joyce recognized and term telomer shall specify a low-molecular-mass product, stated the essentials of the process of telomerization [19]. the end groups of which are the X and Y fragments of a "Telomerization" is defined as the process of reacting, telogen XY. under polymerization conditions, a molecule XY which Since 1948 a great deal of work hat been carried out is called a "telogen" with more than one unit of on the telomerization process, both fundamental and of a polymerizable compound having ethylenic unsaturation more applied nature. In particular the ethylene-carbon called a "taxogen" to form products called "telomers" tetrachloride system has been extensively investigated and
having the formula Y(M)nX wherein (M)n is a divalent has been reviewed in great detail by Starks [20]. Recently radical formed by chemical union with the formation of the chemical-initiated telomerization of VCA was reported new carbon bonds, of n molecules of taxogen, the unit M by Tamura, Kunieda and Takizawa [21, 22). These workers PER-11-9 fji.''tO 'nit the '.e'omerization C VCA il) with a variety of k,iR"K 'j()'yuid;ocienom"thar'« as teiogens could b" effected by •- k iY')2+k (Y)(YMj)+k 3(V')(YM2)+ . . . e ther of th.' free-radical initiator? benzoyl peroxide (BPO) t1 t2 t O! azooisisobutyronitníe (AIBN), as shown below. However, the use instead of the generalized term kt(R')2 greatly simplifies the final kinetic expressions. With the aid of the steady-state theory, equations
r describing the YMn species are f i st developed, V" v d(YMj) dt
f o- eKair.Di'';, wtve oadjci' tetrachloride was used as the •-•ka(M)(Y')-kp1(M)lYMj)-kf1(XY)(YM^-kt(YMj)IR') tt'.og..T f'-.r.-re wa^ isolati-"-; end identified -0 'i-c'-lo'u 5-tnct:iororrethyl-1,?-dioxolan-2-one (4) an;! the (YMi) p-?, C, and 4 te'omers The n-2 teiomer product was '•.•solved into two conformers, trjni-jn!i-rrvris (5) and kJMlíY') .(1)
:rjnf-r,r-trans (6i. The n 2 'ieioiner conformers were kp1(M)+k(1(XY)+ktIR') converted to 5 deoxv-r.'/xylose (7) and 5 deoxy-t/'-lyxose (Ri derivatives by means of acid hydrolysis. The reaction Likewise, Mnitics of the telomerzation of VCA was net reoorted.
dlYMj)
dt "T ^"7 kp1(lvD(YMi)-kp2IM)(YM2)-kf2(XY)(YM2)-k.(YM2)(R') 'X' On 0
k Cv1)(YMj) p1 .(2)
kp2(M) (k,2(XY)+k,(RÏ
By substitution of (YMi) from equation 1 into equation 2,
(YMÓI A •• investigator of flu; iadialion induced k k (M)2(V) teinrnen/a'ion of VGA would thus srxrr in order, a p1
particularly from a fundamental point of view in that thtre (kp1(M!+kf1(XY)+k,(R) Mkp2(iVt)+k(2(XY) fk,(R) ) have bet»", few attempts at experimental verification of the complex rate equations defining the telomerization process. In like manner it may be shown that Also the chain-transfer coefficients have not been determined for any VCA telogen system. (YM„,
n 1 ka(M) (Y-)n"' kpi 5.2 Telomerization Kinetics .(3)
n"(kpj(M)+kfi(XY)+ktIR') ) The radiation-induced telomerization process can be represented by the followinn reaction schemr where XY telcgen and M" monomer. If we let Rat^
Imf i.itirm XY • X' . V R
Propagation Y - M • YM, ka (MM Y) n 1
YM'i - M • YM7 k (lvl)(YMi) (M) n* kpi pl .(4)
/M M • YM3 k„2IM)(YM2) 2 II^kpjIMI+kfjIXYI+kjIR't )
YM3 • M • YM4 k[)3IM)(YM3)
YM„ M • YM,.., k ,(M!IYMn) pr Then we may write the following: Ct- .li" Tra'r !:•: vv, /Y • YM,X Y' knIX7)IYM',)
XY • YMjX t Y kptXY)(YM ) •f'fi-2 2 IYM1)
xy YIV3 • /M3X -t Y fc^lXrdlYV^) .(5) XY YMn • YfJ!„X • / kfn(XY)'YMn)
1 ÍT 'Ti:r,.>Tior 2R • Produc» k.(R')2
IN Y or YM„) It must be realized that the termination reaction as In a similar manner the concentration of the teiomer radical •M'I ' •• 1 vir'.ition, (Y) may be found: PER11-10 d«Y') Equations describing the rate of formation of the telomer — dT oroducts may be written as follows: = R-k (M)(Y)-k (YKR )+k (XYHYMj) + ... a t f1 dtYA^X) = 0 dt d(Y) = kfl(XY)(YM^) dt dlYIW^Xi = R-k,(MKY)-k (Y)(R)+(XY)Z7k (YMfl t (j di
= 0 kaknR(M)(XY) dlY)
(kpl(M)+kf1IXYI+k,(R))(ka(M)+kt(R")-ka(XY)27l k = R-k,(M)IY">-ktIY')(R)+ki(Y>tXY)27 fiZi Likewise, = 0 d(YM X» (Y) 2 dt R (6) = kf2IXY)(YM2> k ka(M)+kt d(YM2X) Art equation for the rate of monomer consumption may be dt written as follows: k k R(M)z(XY)k -d(MI a J2 p1 dt ,t (ka(M)+k,(R')-ka(XY)Z7 fiZi>ni(kpi(M)+kt(R')+kfiIXY») k M YM 7 (ID = kaIM)(Y)+27 pil " i' < > By substitution of equations (5) and (6) into equation (7) In like manner the generalized form of the telomer rate there is obtained equation may be shown to be -d(M) dt dt k n-1 kaR(M>+kaR(M)£7 piZi kgk^RllwHXYin," k j k z ka(M)+k,(R)-ka(XY)S7 fi i lkaIM)+kt(R')-kaIXY)Z7 kfiZi)n"(kpj(M)+k1(R')+k ,/j /l kaR(M)M + Z7kpiZj) kj R which can be obtained by equating the total rates of .(8) k i radical formation and termination. Thus, by substitution, ka(M>+kt(R)-kaIXY)S7 fiZ the term kt(R') becomes k^RA Similarly, a rate expression for the rate of telogen The mole fraction of the first telomer with respect to consumption may be derived as follows: the entire telomer product is termed F-j and can be defined a, the ratio of the rate of formation of the first telomer to -d(XY) the rate of form.-tion of all telomer products, and may be dt expressed by equation (13) [23]: = R+(XY)l7' d(XV) kf1(XY)(YMi) -d(XV) .(13) dt kf1(YMi)(XY)+kpl(M)IYM^) k R+ka dt k(1(XY) k (XY)+k (M) k RIXY)Z7kfiZj M Pin1 ' = R+_. f k^MI+kjIR'l-k.IXYlE, kfiZj (k /k )(XY)/(M) -dIXY) f1 p1 (kf1/kp1)(XY)/IM) + 1 f k^XYlZ,^ I k C^R L kaIM)+kt(R')-kaIXY)r7 fiZiJ .(9) CiR + 1 .(14) PERU ii where R is the telogen to monomer ratio, (CCl4)/(M), and In a similar manner it can be shown that Ci is the first chain-transfer coefficient and represents the ratio kf| kpl- Since the fraction of total telomer products higher than the first telomer is 1 —F-j. and of this amount dlYM,n + 1X ) the fraction which is second telomer is C2R(C2R+D. the mole fraction F2 of the second telomer is given by equation = C„R+- (19) 115): r2 It is clear from the above discussion on (1^ F,ic n telomerization kinetics that the rate expressions for the 2 .(15) C^R change in concentrations of the monomer, telogen and telomer products are extremely complicated. As a result of this complexity it is difficult to predict with certainty After subsequent rearrangement. exactly what should be the numerical relationship between the various reaction rates and the expei imental parameters of r.onomer and telogen concentrations, and irradiation C,R dose rate. If numerical values for the individual rate .06) (C^R + IXCjR+D constants were available, the rate expressions could be solved numerically. However these values are not available In the case of vinylene carbonate. An indication of the In like manner the generalized form is as follows: validity of these rate expressions may be obtained by a comparison with the corresponding empirical relationships based on experimental data. C„R .(1/) n 5.3 Results and Discussion n^CjR+D The value of this approach is that, given the Initial experiments on the radiation-induced experimental parameter R and telomer product distribution telomerization of VCA were carried out using carbon ratio, the idevant chain transfer coefficients may be readily tetrachloride, chlooform, methylene chloride, Freon 114, calculated. Just as the monomer reactivity ratios n and r2 and methyl iodide as potential telogens. With the exception define the product composition in a copolymerizaticn of methyl iodide, all of the abovementioned telogens process, the chain-transfer coefficients define the molecular yielded telomer products. In the case of methyl iodide, mass distribution of a telomerization process for any given presumably hydrogen iodide, an excellent free-radical set of experimental parameters. scavenger, is produced djring irradiation which effectively inhibits free-radical chain processes. Due to the lack of The chain-transfer coefficients can also be calculated confusing side reactions, carbon tetrachloride was selected directly from the rates of telomer formation. For example as the nlogen of choice. the ratio of the rate of formation of the first telomer with respect to the second can be shown to be In one experiment carried out at 75 °C, an irradiation dose rate of 2,7 kGy/h, and with a telogen/monomer d(YM,X) concentration ratio of 4,0, a crude reaction product was obtained. Separation by column chromatography on silica d(YM2X) gel afforded the n=1 adduct 4, the trans-anti-trans 5 and ^ kJl k„,(M) +k,,(XY) +kl/2 HVl\ trans-syn-trans 6 n=2 telomers. The n=1 adduct 4 was P subjected to micro-distillation affording a white crystalline kp1k(2(M)|_ J solid, m.p. 48-50 °C (lit. (22] 53-54 <>C). The two n=2 And where (k (lv1)+k 2 k k k 10,74 respectively. The flame response for VCA was 3,60. f1 p2 + f1(XY) A quantitative analysis of each irradiated telogen monomer k k k (M) p1 f2 p1 sample was carried out by means of GC, using nitrobenzene dlYIV^X) as the internal standard. d(YM X) 2 Tne radiation-induct d telomerization of VCA with carbon tetrachloride was carried out at an irradiation C,R (18) temperature of 75 °C and at a dose rate of 2,7 kGy/h, *nd I PER 11 12 the telogen/monomer concentration ratio was varied from of formation of the n=1 adduct 4 and the two n-2 telomers 4,0 to rO.O. In Figure 10 and 11 art seen the results where 5 and 6 are strictly linear functions of irradiation time. the telogen/monomef concentration ratio was 15,0. The Although the telogen concentration is relatively constant rate of monomer depletion is not a linear function of due tc its large excess, the monomer concentration clearly reaction time and is relatively independent of the decreases at a rapid rate during the course of the telogen/monomer concentration ratio. However, the rates telomerization process. Thus we may conclude that the rate 75- SO * 25 Run Tim» Ih) Fig. 10. Rate of depletion of vinylene carbonate at 75 oc and at a dose rate of 2,7 kGy/h. The telogen/monomer concentration ratio was 15,0. 30 - J t 2 3 Rxn Tim» (h ) Fig. 11. Plots of(O) rate of formation of the n=1 adduct, (9) of the total n=2 telomers, and (D, A> of the Individual trans-anti-trans and trans-syn-trans n=2 telomers. V*- __^ PER 11 13 of n=1 adduet and n=2 tdomer formation is independent of concentration. As shown in Figure 12, the total rate of monomer concentration. In Figure 12 the rate of formation formation of the r»=2 telomere 5 and 6 is nearly of the n=1 adduct and the total rate of formation of the independent of the tetogm/monomer concentration ratio n=2 telomere 5 and 6 are plotted as a function of the and is therefore also independent of the telogen telogen/monomer concentration ratio over the range from concentration. We may therefore establish the following 4.0 to 20.0. The rate of formation of 4 is dearly a linear relationships: function of the telogen/monomer concentration ratio. Since the rate of formation of 4 has been shown to be 1— a (MftXY)1 and -L_ ^ (M)°IXY)° independent of the monomer concentration, we may dt dt conclude that it is directly proportional to the telogtn 12.5 n«1 Adduct Slope. 0.50 10,0 ~ 7.5 i x sS 5.0 n«2 Ttlomtrl total) Slope s 0,05 23 10 15 20 (CCUI/IVCA) Fig. 12. Plots of (o) rate of formation of the n=l adduct and (•) of the total n-2 ttlomers as a function of the telogen/monomer concentration ratio at 75 °C and at a dose rate of 2,7kGyfh. PERU 14 In Figure 13 the ratio d(YMiX)/d(YM2X> is plotted respect to the integer n is due only to field effect* between as a function of the telogen/monomer ratio. From equation the telomer radical end group Y, and the telogen XY, then 18 it may be seen that the line slope is equal to the value of the interaction should be due to Coulomb;" repulsion the first chain-transfer coefficient, that is C\ - 0,116. The forces between the two species. Using this approach and the line intercept extrapolated to (XY)/|M) - 0 yields the value assumption that the distance between Y and XY in the of 0,337 for the ratio Cj/C2- From this value it may be transition state is proportional to the number of bonds calculated that C2 = 0,34. Thus we observe that the ratio of between Y and XY, that is the distance is proportional to the rate of chain transfer to propagation is greater for YM2 2n+1, then the following equation may be derived [24]: than for YM-j. A study of Dreiding stereomodels of the two ntl l09 C5= 13,3, and Cmf = 13 (25]. If the variation in Cp with atoms in the VCA molecule. 3|- a Slopt =0,116 s £ Intersection at ICC1AI/IVCA)- 0 is 0,337 _L 5 10 15 20 (CCU)/(VCA) Fig. 13. Ratio of the rates of formation of the n=J adduct and total n=2 telormrs as a function of the telogen I monomer concentration ratio at 75 °C and at a dose rate of 2,7 kGy/h. PERU 15 The functional relationship bttwttn tht rata of 1. For the n=' adduct a value of 0.38 is reasonably dost to formation of the n=1 adduct 4, the total rate of formation a value of Vi, but a value of zero for the n=2 telomtr cannot of the n=2 telomers 5 and 6 and the radiation intensity, is be easily explained. illustrated in Figure 14. At an irradiation temperature of The relationship between tht rates of formation of 75 °C, a tetocen/monomer concentration ratio of 9.0, and the n=1 adduct 4 and n=2 ttlomtrs 5 and 6 and irradiation over a dost rate range of 1,4 to 7,5kGy/h, there was temperature was also determined. From tht Arrhtnkis plot calculated a 0,38 order relationship between d(YMjX)/dt in Figure 15, an activation energy for tht formation of t*>e and radiation intensity I. and a zero order relationship n=1 adduct 4 of 17.6kJ/molt was calculated. For the between d(YM2X)/dt and I. Thus tht relationship between formation of tht n=2 ttlomtrs 5 and 6 an activation energy tht rates of formation of tht n=1 adduct and total n=2 of 64.9 kJ/mole was obtained. telomtr as a function of telogtn and monomer Tht results obtained for the VCA-carbon concentrations, and irradiation dost rate has been tetrachloride system raise the possibility that tht classical determined to be teiomtrization scheme does not properly explain tht above experimental results. Unfortunately tht VCA-carbon 20 nsl Adduct IS Slop* = 0.38 s- w £ -—-°'*"* *o— z t0000 % •- — g)~ w n» 2 Ttlofntr £ 5 ~&~00~^ Slop» s 0,05 or. 1 2,5 5.0 7,5 10 KkGyrT Fig. 14. Plots of (o) rate of formation of the n=J adduct and (•) of the total m*2 telomers as a function of Irradiation Intensity at 75 °C and'at a telogen/monomer concentration ratio of 9,0. PER-11-16 10 75 n = 1 Adduct Ea = 17,6kJ/moie 3* 5.0 Z n s 2 Ttlomcr Eo:6t.9kJ/mole 2,5 2.6 2.7 2.8 ;,9 10" T Fig. 15. Plots of(">) rate of formation of the n-l adduct and (•) of the total n=^2 telormrs as a function of irradiation temperature ct a dose rate of 2,7 kGy/h. The telogenjmonomer concentration ratio was 9,0. Another approach is to consider a system such as VCA-bromotrichloromethane. Bromotrichloromethane (BTCM) is a much more reactive chain-transfer agent than carbon tetrachloride |22] and if we assume that kf-j > kpi, we may write the following reaction sequence which leads to equation (21): R'^IMI R3t£ (21) XY- •X f Y R Thus it would appear that the use of a very reactivt; Y •YM, + M • k„(M)(Y') chain-transfer agent such 3i BTCM could result in a great »YM, X + Y' YM; + XY- kt1(XY)(YMj) simplification of the normally complicated telomerization •Product 2 rale expression',. Also with piopcr control of the 2R- kt(R) u iJ PER11-17 telogen/monomer concentration ratio the reaction between addition would allow the determination of a specific rate VCA and BTCM could be forced to produce only th* n-1 constant such as ka. In addition, appropriate variation of adduct and n-2 telomers. Irradiation of 2 VCA BTCM the telo Hn/monomer concentration ratio might permit the mixture with a telogen/monomer concentration ratio of 3,0 selective generation of a limited number of telomer resulted in the exclusive formation of the n=1 adduct. products, thus greatly easing the analysis problem Although the rate of depletion of VCA appears nonlinear encountered in the VCA-carbon tetrachloride system. and the rate of formation cf the n=1 adduct linear (m.p. 47.5-48 oc (lit. (22] 51-52 °C), K=6.57 for nitrobenzene 6. 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