On the participation of cyclic molecules in the formation of molecular weight distribution of oligodiethyleneglycol adipate

F o r m a t i o n of M W D of oligodiethyleneglycol a d i p a t e

1745

11. Yu. A. SHLYAPNIKOV, V. B. MILLER, M. B. NEIMAN a n d Ye. S. TORSUYEVA, Dokl. A N SSSR 151: 148, 1963 12. I. A. SHLYAPNIKOVA, V. B. MILLER and Yu. A. SHLYAPNIKOV, Vysokomo1. soyed. 14B: 526, 1972 (Not translated in Polymer Sci. U.S.S.R.) 13. T. V. MONAKHOVA, T. A. BOGAYEVSKAYA a n d Yu. A. SHLYAPNIKOV, Vysokomol. soyed. 16B: 840, 1974 (Not translated in Polymer Sci. U.S.S.R.) 14. A. P. MARYIN and Yu. A. SHLYAPNIKOV, Vysokomol. soyed. 17B: 582, 1975 (Not translated in Polymer Sci. U.S.S.R.) 15. I. G. LATYSHKAYEVA, G. P. BELOV, T. A. BOGAYEVSKAYA and Yu. A. SHLYAPNIKOV, Vysokomol. soyed. 16B: 890, 1974 (Not translated in Polymer Sci. U.S.S.R.) 16. L G. L A T Y S H K A Y E V A , G. P. BELOV, T. A . BOGAYEVSKAYA and Yu. A . SHLYAPNIKOV, Vysokomol. soyed. 19B: 375, 1977 (Not translated in Polymer Sci. U.S.S.R.)

Polymer ScienceU.S.S.R. Vol. 21, pp. 1745-1754. © Pergamon Press Ltd. 1980. Printed in Poland

0032-3950/79[0701-1745507.50/0

ON THE PARTICIPATION OF CYCLIC MOLECULES IN THE FORMATION OF MOLECULAR WEIGHT DISTRIBUTION OF OLIGODIETHYLENEGLYCOL ADIPATE* A . A . GURYLEVA D . 1~. SHARAFUTDII~OVA a n d B . YA. TEITEL'BAUNI A. Ye. Arbuzov I n s t i t u t e of Organic and Physical Chemistry, U.S.S.R. A c a d e m y of S c i e n c ~ (Received 29 J u n e 1978) The establishment of an equilibrium M W D b y heating for up to 500 hr a t 180 ° have been investigated b y t u r b i d i m e t r y , ebulliometry, I R spectroscopy, etc., t a k i n g as an example the fraction with ~/n-~ 1800 (I) which was separated from oligodiethyleneglycol a d i p a t e and does not contain cyclic molecules, a n d mixtures of I with t h e monomeric cyclic ester (II). The mixtures contained compounds I a n d I I in the weight ratios of 1 : 2 (III) and 2 : 1 (IV). Oligomer I I itself polymerizes under these conditions in the presence of a d m i x t u r e s of water and forms chains ending in OH and COOI~ groups with a functionality o f f , : 1 calculating for OH groups. Ring opening of ester I I in the presence of oligomer I leads to the formation of bifunctional (in respect to the hydroxyl) molecules. The heating of compound I is accompanied along with interchain exchange processes b y intramolecutar reactions involving the cleavage of cyclic molecules, which is reflected in lower values of ~ n and j n compared with the initial values. A similar level of fn (1.6-1.8) was likewise found in mixtures of I I and IV with a n initial excess content of cyclic monomer a n d with low values o f f ~ . The sum t o t a l o f interchain and intrachain reactions leads to oligomers having a certain equilibrium d i s t r i b u t i o n of linear a n d cyclic (not only monomeric) molecules. * V:fsokomol. soyed. A21: No. 7, 1585-1592, 1979.

1746

A.A.

GURYImVA e$ al.

IT I8 well k n o w n t h a t p o l y c o n d e n s a t i o n p r o d u c t s f e a t u r e equilibrium a r r a n g e m e n t s o f MWD. I n t e r c h a i n exchange leading in t i m e t o a widening o f the M W D , likewise until t h e equilibrium s t a t e is established [1], takes place a t sufficiently h i g h t e m p e r a t u r e s in n a r r o w fractions s e p a r a t e d f r o m t h e foregoing p o l y m e r s . H o w e v e r , p o l y c o n d e n s a t i o n p r o d u c t s contain cyclic molecules as well as l i n e a r macromolecules; a definite c o n t e n t o f cyclic molecules is to be f o u n d in e a c h e q u i l i b r i u m p o l y c o n d e n s a t i o n polymer. Cyelization influences t h e t o t a l functiona l i t y o f p o l y c o n d e n s a t i o n products, a n d plays a m a j o r role in t h e utilization o f oligoestors containing r e a c t i v e e n d g r o u p s used for t h e synthesis of high-molecu l a r compounds. T h e " c y c l i c " f r a c t i o n in a n oligomer represents the t o t a l n u m b e r o f cyclic molecules of v a r y i n g (normally quite low) molecular weight (monomers, dimers, trimers, etc.) forming a characteristic distribution [2]. This has b e e n d e m o n s t r a t e d , in particular, for p o l y d i e t h y l e n e g l y c o l a d i p a t e [3]. T h e p r o b l e m o f t h e i n t e r a c t i o n of linear moleculo~ w i t h cyclic ones is o f m a j o r in~ terest, since this i n t e r a c t i o n influences molecular characteristics a n d the r e a c t i v i t y o f t h e oligomers. T h e p r o b l e m is considered in the present work, the aim of which was t 6 o b s e r v e processes o f f o r m a t i o n o f M W D of oligomers u n d e r conditions of a n excesa a m o u n t o f cyclic molecules i.e. a specially i n t r o d u c e d cyclic ester. I n this case processes o f ring opening a n d o f i n t e r c h a i n exchange o u g h t to t a k e place simultaneously. We studied the fraction with ~ = 1 8 0 0 , ~w/~rn=l'41 (T) separated from the oligodiethyleneglyeol adipate (ODEGA) and the monomeric cyclic ester (M=216) having th~ structure O=C--CH~--CH~--CH~--CIt~--C=O / \ O--CH~--CHI--0--CH~--CHI--O

(II)

Use of the linear component of the above fraction instead of the ordinary unfractionated ollgomer was dictated by the fact that, in contrast to the latter, it contained no low molecular cyclic compounds. The ODEGA was the commercial product prepared by polycondensation of diethyleno glycol and adipic acid (with an excess of diethylene glycol); it is characterized by ~ n = 900~ polydispersity coefficient U-~lw/IV4n=1"57 and number average functionality f n = 1.78. A study was made of the cyclic ester mixed with the ODEGA fraction, weight rati(~ o f t h e c o m p o n e n t s 1 : 2 (III) with/~7/~-----536and 2 : 1 (IV) with ~7/n~304. Each of the mixtures was placed in a series of test-tubes, sealed unde rvacuum (residual pressurenot exceeding 10 -a torr) and thermostatted at 180°. At the end of fixed intervals of time the test-tubes vcere opened one by one and the contents analyzed: the MW]:) was investigated, ll~n was determined by ebullioscopy in benzene, and the number of OH groups determined by I R m-lalysis, using the method of [4]. On the basis of these data we calculated the functionality and the amount of "non-functional" cyclic fraction in the system. The number average~ functionality jn is the ~'n/~/equtv ratio obtained respectively from the results of ebulliometry and IR spectroscopy. The IR spectra were recorded on a UR-10 spectrometer in THF. The MWD was investigated, by turbidimetric titration, using saturation equationa derived from the preparative fractionation results [5]. Fractionation was carried out by" elution from a thin film on dispersed molybdenum glass in a column at 25°; the solvents were methyl ethyl ketone (MEK) or methyl butyl ketone (MBK), with n-haxane or heptano ms the precipitants.

F o r m a t i o n of M W D of oligozliethyleneglycol adipato

1747

A n automatic recording device [6] was used to record the turbidimctrie curves. The initial concentration of solutions undergoing t i t r a t i o n was {1-5)× 10 -2 g/dl, precipitanh feed rate, 0.32 ml/min, stirring rate 360 rev/min. The solvent-precipitant system used b y us was ~_EK-petroleum ether (the fraction with boiling limits 75-100 °, n~° 1.3748). On a previous occasion the following saturation equation was derived for ODEGA in the l a t t e r system y , = 1.50--0.11 log c,--0.32 log M~, (17 where y~ is the volume fraction of precipitant; c, -- the polymer concentration; M~ -- ther molecular weight of the p o l y m e r precipitated a t the ith point,. However, it was found more convenient to work with an individual compound (n-hexane); the equation derived for the l a t t e r case was y~= 1.48--0.116 log c~--0-31 log M~ (2) I n the turbidimetric analysis of products obtained b y heating compound I I and mixtures of I I I and IV, the initial cyclic monomer and the other cyclic molecules of low MW dc~ not separate out of solution. In view of this the solution concentration was selected t a k i n g the portion precipitated into account. To do so the weight of the cyclic fraction determined from the value of fn was deducted from the sample weight. As the reaction proceeds, t h e a m o u n t of the cyclic fraction is reduced to 5 w t . % , i.e. it becomes insignificant, and does n o t cause a n y significant change in the solution concentration (it must, however, be allowed for in the early stages of the reaction). The MWD curves and the average molecular weights calculated from the t i t r a t i o n curves using equations (1) a n d (2) were c o m p a r e d wit~l results obtained by independeflt methods, ebulliometry, fractionation, and, in individual cases, light scattering and g.p.e. as well. Ebulliometric determinations were carried out on a modified R a y a p p a r a t u s provided with a twenty junction thermocouple. Light scattering measurements were carried out in M E K using a Sofica instrument (made in France). Gel chromatograms were obtained with the aid of a Waters-200 device in T H F ; columns containing styrogel were used, and catibra, tion was carried out with polystyrene standards. To check the initial components the l a t t e r were k e p t a t 180% as were the mixtures, a n d were analyzed after the same periods of time h a d elapsed.

The oligoester fraction with f~n=1800 (I). T a b l e 1 a n d F i g . 1 g i v e d a t a orL changes occurring in the molecular characteristics of the fractions during heati n g a t 180 °. I t c a n b e s e e n t h a t t h e h e a t i n g p r o c e s s l e a d s t o a w i d e n i n g o f t h e M W D a t 180 °, a n d t h e p o l y d i s p e r s i t y c o e f f i c i e n t U r i s e s f r o m 1.4 i n t h e i n i t i a l s t a t e t o 2.0 i n t h e e q u i l i b r i u m p r o d u c t . O n a t t a i n m e n t o f t h e e q u i l i b r i u m s t a t e a f t e r -- 100 h r ] n is r e d u c e d f r o m a n i n i t i a l 2.03 t o 1.6, a n d Aln f r o m 1800 t o 1320. T h e s e t w o f a c t s a r e a c c o u n t e d f o r b y t h e f o r m a t i o n o f c y c l i c m o l e c u l e s (of " z e r o ' " f u n c t i o n a l i t y a n d l o w ATn) a m o u n t i n g t o u p t o 5 w t . % . * In oligomer I cyclic products may be formed as a result of a sort of intramolecular transesterification, when the terminal hydroxyl interacts with one of the ester bonds of the same molecule

I -C--O~OH nJ

~=0

+ HO

OH

I--OH * According to the g.p.c, results oligomer I in its original state contains no rings. This is: likewise evidenced b y the value of fro.

A. A. Gv-R~clmvAe# al.

1748

Ester bonds located in the flexible chain at varying distances away from the .attacking h y d r o x y l m a y be involved in the reaction. This is reflected in the formation of rings containing varying numbers n of elementary units R and in a ~corresl~ondingly varying degree of shortening of oligodiol molecules. Since the reverse process m a y also occur during the interaction of oligodiol OH groups ~with cyclic molecules containing ester bonds, a definite equilibrium is established in the system between linear and cyclic molecules. The cyclization is basically identical to the interchain exchange reactions involving a typical ester exchange reaction. However, there is a major difference in t h a t "ordinary" exchange does not lead to a n y change in the number of par• icles, and the value of/l~n remains constant, whereas the number of particles is increased as a result of an intramolecular reaction, and the value of JtT~ is reduced. I t is characteristic t h a t the heating of equilibrium oligoesters under • he conditions in question does not lead to a change in/l~n or in f n . This means t h a t the number of cyclic molecules in the oligoesters remains constant. The cyclic ester (If). Polymerization of ester I I at 180 ° yields an oligoester ~ i t h ~ n ~ 2 0 , 0 0 0 (Fig. 1). As the reaction proceeds the cyclic ester content is reduced, and the functionality rises, changing from zero at the start of the react i o n to a value close to unity a~ the end. This can readily be understood, bearing i n mind a possible mechanism of polyester formation. Ring opening in the prim a r y step takes place under the influence of traces of water; our own observations as well as information published in literature regarding similar cases [8] ~how t h a t compounds that have been painstakingly dried~fail to polymerize. ~rhe hydrolysis product of cyclic ester I I is a h y d r o x y acid containing terminal O H and COOH groups 'C0[ ÷ H~O-~HO--B--C00H, where R~--(CH,)s--O--(CH,),-,O--CO--(CH,),-I

T h e process m a y then be represented either as a polyesterification of t h e resulting h y d r o x y acid HO-- R-- COOH • HO -- R -- COOH-, HO-- R-- COO -- R-- COOH + H,O •~the water evolved is consumed in the opening of new rings), or as polyaddition .~f ester I I to a h y d r o x y acid [9] Co -J- 0

-~, H0 ,~ C00H ---*H0--H--C00

C00H

A similar mechanism is involved in the hydrolytic polymerization of lactams

Formation

o f M W D oI o l i g o d i e t h y l e n e g l y c o l a d i p a t e

174~

i[10] and of a cyclic trimer of ethylene terephthalate, leading to the formation of a linear product [9]. Thus there is no difference in the chain structure of the 0DEGA synthesized in the normal manner compared with that prepared from cyclic ester II, bu~ there is a difference in regard to the endgroups: in the latter case the IR spectrum has the band relating to the OH group at 3450 cm -~, the intensity of which is reduced, and, in a:ldition, a band in the 3100 cm - ' region pertaining to the COOH group (Fig. 2), while the spectrum of the normal oligovster with terminal OH groups does not contain the latter band. Since equivalent weight determinations involving the IR spectra are calculated on the basis of the band pertaining to the .OH group, the functionality of the polymerization product of II is lower b y one-half. *tABLE l .

EFFECT

OF HEATIlffG

1780 1745 1390 1320 1320 1350 1320

877 881 848 825 825 829 825

ODEGA

Number of rings, mole%

~.~.

Time, hr

0 30 75 100 165 350 480

AT 180 ° O~¢ THE

2"03 1"98 1"64 1"60 1"60 1"61 1"60

0 1.00 18.0 20"0 20-0 19.5 20-0

FRACTION WITH ~ n = 1 8 0 0 0

Turbitimetric

data

M~/M. 1730 1625 1575 1500 1610 1515

16001

2480 2500 2900 3100 3360 3060 3260

1-41 1.54 1-84 2.06 2.08 2-02 2-03

* According to the g.p.c, results .~'~=1760, M~=2300, M,/M,=I.30; it was found by the light scattering m~tho4 that / ~ t = 2500. Note. M~ was calculated from the ebuiliometric data, and ~J~,q,l,. from the IR spectroscopy data.

The stoichiometry of the transformation of compound II to the linear chains of an oligo acid with Mn ~ 2000 requires the participation of an equimolar amount o f water, i.e. approximately 1 wt. %. An excess of water may lead to the formation of shorter chains. A special investigation of the polymerization of ester I I in the 15resence of fixed amounts of water showed that the latter affects the polymerization rate and the molecular weight of the oligomer. Given an H~O content of 1 wt. %, the equilibrium state is established in the system by the end of the period of temperature control (480 hr), and is characterized by Jl~n=-1600 and U----2.09; in the case of an HzO content of 2-5 wt.% the equilibrium product is obtained already in 150 hr, but has/~n=600 and U----1.5. The NIWD of the oligoester prepared from compound II was determined b y turbidimetric titration. The coefficients of the saturation equation for the oligoester in question were the same as in eqn. (2), so that the latter could be used to find the MWD arrangements of all the oligoesters under study. The MWD characteristics for the polymerization p:oducts of monomer I I

A: .A. OURYLEVA e$ @l.

1750

given in Table 2 for different stages in the process. I t can be seen t h a t changes occurring in the MWD during the reaction are similar to those observed in t h e c a s e of polymerization o f cyclic oxides [11, 12]./l#n rises during the reaction in view of the ljn~Hug of compound I I to the oligomer chains: However, intermolecular and intramolecular reactions of the type discussed above become possible as the chain lengthens. These reactions take place because of the p r e s e n c e of the OH group at one of the chain ends. are

t~n ~/0 -3

a

•0

•II

1"2

xx

=

I

f

O.

I

100

300

500

I00

,

I

300

,

]

500

T i m e , hr

FIG. i . Plots of ~n (a) and ]n (b) vs. time of heating at 180°: 1--ODEGA fraction, in the o~iginal state containing no cyclic molecules; II--monomeric cyclic ester, III and IV--mixtures of compounds, weight ratios 2 : 1 and 1 : 2 respectively. Intramolecular reactions involving the cleavage of cyclic molecules lead to a qua~t~tive change in the cyclic fraction; n-meric rings must appear in the latter along with the original monomer, the amount of which decreases. T h e s u m tota! o f the processes occurring result in il4n values going through a maximum. In addition, interchain exchange plays a predominating role in the final stages of the, reaction, as m a y be surmised from the absence of change in the values of Mn. A t the e n d o f the process the polydispersity of the product is characterized by a v~lue of U ~ 2 . 3 , which approximates to the result obtained using the column fractionation data ( U " 2.1 ) . ' M i ~ u r e s o f the O D E G A fraction and cyclic esters ( I I I and I V ) . I t could be assumed t h a t the reactions considered above for each of the components (I and II) t a k e place simultaneously i n mixtures of I I I and IV. I t was found, however, t h a t transformation of monomer I I to linear chains takes place in the presence of oligomer I in a manner differing from t h a t occurring in the case of the pure monomer, when the molecules formed end in terminal hydroxyl and carboxy! groups. Only OH groups are detectable (within the limits of accuracy, of the spectrum method) in the products obtained as a result of heating the mixtures; hands,relating to COOH groups are not found in the I R spectra (Fig. 2). This means t h a t ring oTening in compound I I takes place under the action o f the oIigoester molecules without the need for initiation by H20 molecules.

Formation of MWD of oligodiethyleneglycol adipate

.1751

This is accompanied b y ester bond formation, and at the chain ends there are as previously OH groups, with the chain length increasing as a result of the ring opening !

.C=O

II

]

H H 0 ~ OH --~H0--R--C00 ~ OH

Even if it is assumed that the primary step is ring opening as a result of attack by the H 2 0 molecule, the carboxyl end of the resulting hydroxy acid enters into the reaction of esterification with the oligoester molecule. This leads to the formation of a new oligoester molecule lengthened by the size of the m o n o m e r and having O H groups at both ends HO -- R-- COOH + HO~OI-I-*HO-- R-- COO~OH ÷ I-I~O Water formed during the esterification m a y be consumed in the opening of new rings. However, it m a y also be expended in hydrolytic scission of linear chains, which lessens the probability of water affecting rings. I n this case a certain number of chains having a carboxyl endgroup will appear, with the result t h a t both/t~n and f~ values will be reduced.

1

I 30

I

I 34

I

I

38 Y ~ lO - ~ c m - !

:FxO. 2. II~ spectra of the oligoesters (solutions in THF): 1--ODEGA fraction I, 2-4--equilibrium prodhcts of heating compounds II-IV respectively-. As m a y be seen from the curves in Fig. 1, the reaction takes place considerably more rapidly in the case of mixture I I I (Table 3). I t comes to an end in the latter mixture in 250 hr, whereas in mixture IV (Table 4) it is scarcely completed in 480 hr. Moreover a higher value of ~ n is obtained in mixture I I I , and

17b'2

A: A. G V ~ Y L E V A

et at.

the amount of cyclic molecules in the equilibrium product is lower than in th~ case of mixture IV. It follows that the degree of conversion and the ~tT~ valua o f the product are proportionate to the extent to which the composition of th~ reaction mixture approximates to the equimolar composition. TABLE 2. EFFECT OF 1TEATII~rGAT 180 ° O~ CYCLIC ESTER I I

Time, h r

Number of rings, mole Yo

~equlv"

Turbidimetric d a t a

- i

0 30 75 100 165

350 480

204 324 582 767 1670 ~040 .)040

4629 1940 1475 1876 2266 2266

0 0-07 0.30 0.52 0.89 0.90 0.89

100 93.0 70-0 48.0 11.0 10.0 I0-0

1160 1400 1650 1950 2070 1960

~ 2530 3100 3880 4870 5240 4500

2.18 2.21 2.35 2.49

2.53 2.30

Changes in ~ n and ]n for mixture I I I (Fig. 1, curves I I I a and IIIb) follow a s t e a d y course with a minimum in the region of heating for 100 hr. The latter teature of the curves is not~ a random element, as can be seen in the light of re1 8 0 ° O1~ M I X T U R E I I I o F T ~ E C Y C L I C E S T E R O D E G A ~T~ACTIO~ (~rn=1800) i~r THE I~ATIO OF 1 : 2 (2~r~=534)

~ F A B L E 3 . E F I ~ ' E C T O F TtrEATIlffG A T

jr

Time, hr

0 15 50 75 lO0 165 250 350 480

536 750 1470 1500 1250 1600 1830 1860 1820

1531 1563 1035 926 899 1067 1011 1039 995

0"35 0"48 1 "42 1"62 1"39 1"50 1'81 1"79 1'83

Number of rings, mole ~/o 82"6 76"0 29"0 19"0 30"5 25"0 9"5 10"5 8"5

AI~TD T H ~

Turbidimetric d a t a

i

1760 1650 1400 1720 2260 2200 2150

4530 4620 4710 4800 5250 4800 4600

I

--

2.57 2.80 3.36: 2.79 2.32 2.18 2.14

peated determinations as well as the results of experiments carried out at 120 a n d 150 ° . I t is c l e a r t h a t t h e n o n u n i f o r m s h a p e o f t h e c u r v e s m a y s t e m f r o m t h e m u t u a l s u p e r p o s i t i o n o f c h a i n p r o p a g a t i o n (in w h i c h t h e n u m b e r o f m o n o m e r m o l e c u l e s o f I I d e c r e a s e s r a p i d l y a n d M n r i s e s ) o n the" o n e h a n d a n d o f r e a c t i o n s pertaining to the nonequilibrium fraction of oligomer I (leading to reductions in Mn and ]~ down to the respective equilibrium levels, as demonstrated,by curves Ia and Ib) on the other hand. S i n c e t h e r a t e o f c h a i n g r o w t h is s i g n i f i c a n t l y s l o w e r i n m i x t u r e I V , a n d s i n c e the a c t u a l a m o u n t o f o l i g o m e r I i n t h e m i x t u r e is l o w e r b y a f a c t o r o f 4, c u r v e s

Formation of MWD of oligodiethyleneglyeol adipate

1753

I V a and IVb do not reflect processes of transition of the mixture to the equilibrium state (under conditions of a large excess of molecules of low MW). I t is noteworthy that irrespective of the original state (I, I I I or IV) a level ~ o f f n that is, broadly speaking, one and the same (within the limits of 1.6-1.8)~ is established in the system (the exact value o f f a depending on the value of ~ n ) . TABLE

4. ] ~ F F E C T OF H E A T I N G AT 1 8 0 ° ON M I X T U R E I V

O D E G A FRACTIO~ ( ~ . ~ 1 8 0 0 )

Time, hr

0 30 75 100 165

35O 480

~n 290 334 360 380 532 1430 1600

~equiv.

2458 2783 2250 1727 1330 '1067 970

OF T H E

CYCLIC E S T E R A N D ~'li~.~:

I ~ THE I%ATIO OF 2 : 1 (~.----304)

0"118 0"12 0"16 0"22 0"40 1-34 1-65

Number o f rings, m o l e °/o

~5/n

~w

94"0 94"0 92"0 89'0 80'0 33"0 17"5

1380 1470 1230 1800 1700 1750

2424 3300 3360 6400 8300 3530

Turbidimetrie data

1-75 2-24 2-78 3"55 4.91 2-02

I t is evident from this fact that one and the same result comes about through. the various directions of the reaction, i.e. transition of the nonequilibrium fraction (containing no cyclic molecules) to the equilibrium state or ring o p e n i n g under the action of oligodiol molecules in the ratios examined b y us. Quite a different level of f~ is reached, as we have seen, only in the case o f heating the pure cyclic ester II. B u t then the position of the now rising portion of curves I I a and IIb (intermediate between the corresponding curves I I I and IV) m a y at first sight appear irregular. However, this is all attributable to peculiarities of the reaction, which in the case of ester I I involves the formation of oligohydroxy acids (instead of oligodiols) in the case of initiation b y water. I t is clear from the experimental results that this route is not taken in the presence of oligodiols. There is no doubt, however, that the presence of water in the reaction mixture does not help in the preparation of a product of o p t i m a l functionality. It follows from all the considerations discussed above that the m o l e c u l a r composition of the oligoesters under study is formed at sufficiently high temperatures, under synthesis conditions, as a result of a set of interchain and intrachain reactions leading to a definite distribution of linear and cyclic molecules. I f cyclic monomer is removed (by sublimation) from the reaction zone, this d o e s not reduce the amount of the cyclic fraction in the product; the existence of the equilibrium discussed above means that there will be a displacement of the reaction towards the formation of new cyclic molecules. The authors thank 1~. A. Sehlakhter for his kind participation in discussions. of the results. Translated by R . J~ A. I-I~',¢DRy

~754

N.V.

K o z m ~ v ~ I ~ O V a n d A. D. STmeUXHOVIO~r •REFERENCES

1. B. A. BOZENBERG, V. I. I R Z H A K and N. S. YENIKOLOPYAN, Mezhtsepnoi o b m e n v polimerakh (Interehain Exchange in Polymers). p. 20, Izd. " K h i m i y a " , 1975 2. H. JACOBSEN and W. H. STOCKMAYER, J. Chem. Phys. 18: 1800, 1950 3. I. P. TYUPYNDZHYAN, R. A. SHLYAKHTER, Ye. G. ERENBURG and N. P. APUKHTINA, Vysokomol. soyed. 17A: 104, 1975 (Translated in Polymer Sci. U.S.S.R. 17: 1, 116, 1975) "4. K. A. STRECKER and D. M. FRENCH, J. Appl. Polymer Sci. 12: 1697, 1968 ~5. A. P. S H A T E N S H T E I N , Yu. P. VYRSKII, N. A. P R A V I K O V A , P. P. ALIKHANOV, K. I. ZHDANOVA and A. L. IZYUMNIKOV, Opredeleniye molekulyarnykh vosov polimerov (Determination of the Molecular Weights of Polymers). p. 110, Izd. " K h i m i y a " , 1964 ~}. B. Ya. TEITELBAUM and M. P. DIANOV, Zavodsk. lab. 30: 235, 1964 7. A. A. G R Y L E V A , B. Ya. T E I T E L B A U M , R. A. SHLYAKHTER a n d L. P. MOSKEVICH, Vysokomol. soyed. 14A: 1221, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 5, 1370, 1972) 8~ I. GOODMAN and B. F. NESBITT, Polymer 1: 384, 1960 9. V. V. KORSHAK and S, V. VINOGRADOVA, Geterotsepnye poliefiry (Heterochain Polyesters). p. 180, Izd. AN SSSR, 1958 10. V. V. KORSHAK and T. M. FRUNZE, Sinteticheskiye geterotsepnye poliamidy (Synthetic Heterochain Polyamides). p. 81, Izd. AN SSSR, 1962 11. S. Ya. FRENKEL, Vvedeniye v statisticheskuyu teoriyu polimerizatsii (Introduction to the Statistical Theory of Polymerization). p. 186, Izd. "Nauka", 1965 12. E. A. DZHAVADYAN, B. A. ROZENBERG and N. S. YENIKOLOPYAN, Vysokomol. soyed, l l A : 2330, 1969 iTranslated in Polymer Sci. U.S.S.R. 11: 10, 2650, 1969)

Polymer ScienceU.S.S.R. Vol. 21, pp. 1754-1763. PergamonPress Ltd. 1980.Printedin Poland

0032-8950/79/0701-1754507.50/0

THE EFFECT OF ACETONITRILE AND OF DIMETHYLFORMAMIDE ON THE FREE RADICAL POLYMERIZATION OF SOME VINYL MONOMERS* N . V. KOZHEVI~IKOV a n d A. D. STEPUKHOVICH N. G. Chcrnyshevskii State University, Saratov

(Received 3 July 1978) The main l~inetic characteristics have been obtained for the polymerization of ~tyrene, methyl methacrylate and methyl acrylate in acetonitrile and dimethylformamide solutions, with azoisobutyronitrile (ABN) and benzoyl peroxide as initiators. -It is shown t h a t a solvent affects the rate of polymerization initiation b y ABI~, as well a s other stages of the process, which leads to a relationship between rate constants &p/kt~ a n d the monomer concentration, a n d to a deviation of parameters of the total •~* Vysokomol. soyed. A21: No. 7. 1593-1600. 1979.