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Kinetic investigation of the initiation of tetrahydrofuran polymerization by the system BF3-propylene oxide
2376
G . N . KO~RATOV et aL
5. N, N. MAKAROVA, Dissertation, 1971 6. V. S. PAPKOV and G. I,. SLONIMSKII, Vysokomol soyed. 8: 80, 1966 (Translated in Polymer Sei. U.S.S R 8: 1, 84, 1966) 7. S. N. ZHURKOV and E. Ye. TOMASHEVSKII, Sb. Nekotorye problemy prochnosti tverdogo tela (Some Problems of the Strength of Sohd Substances). I z d A N SSSR, 1959 8. Yu. P. KVACHEV, V. S. PAPKOV, V. Yu. LEVIN, A. A. ZHDANOV, G. L. SLONIMSgll and K. A. ANDRIANOV, Dokl A N SSSR 215: 4073, 1974 9. K. A. ANDRIANOV, G. L. SLONIMSKII, D. Ya. TSVANKIN, V. S. PAPKOV, V. Yu. LEVIN, Yu. P. KVACHEV, M. N. ILYINA and N. N. MAKAROVA, Vysokomol. soyed. B16: 208, 1974 (Not translated in Polymer Scl. U.S.S R ) 10. Yu. P. KVACHEV, I. I. PEREPECHKO, V. S. PAPKOV, V. Yu. LEVIN, A. A. ZHDANOV, G. L. SLONIMSKII and K. A. ANDRIANOV, Mekhamka pohmerov, 804, 1973 l l . C. L. FRYE and J. M. KLOSOWSKI, J. Amer. Chem. Soc 93: 4599, 1971
KINETIC INVESTIGATION OF THE INITIATION OF TETRAHYDROFURAN POLYMERIZATION BY THE SYSTEM BFs-PROPYLENE OXIDE* G. N. KOMRATOV, R. A. :BARzYKI~A, G V. KOROVI~A and S. G. EI~TELI8 Chenncal Physics Institute, U.S.S.R. A c a d e m y of Scmnces (Recewed 7 August 1974)
A kmetm s t u d y was made of changes in the concentration of propylene oxldo m the polymerLzatlon of tetrahydrofuran initiated b y the system BFa-propylene oxide, using the g.l.e, method. Tt m shown t h a t consumption of the ~-oxlde proceeds in accordance with a first order law. This is a p p a r e n t l y due to the effect of reactions of lmaltatlon of chain growth, whmh are aecompamed b y the regeneration of BF3. Within the period of time examined the BF8 concentratmn m a y therefore be taken to be constant and equal to [BFs]0. The rate of lmtlatmn was determmed (k~--~5 5 L/mole. see).
VERY little study has been made of the imtiation stage m the polymerization o f tetrahydrofuran (THF) under the action of B F 3 in the presence of e-oxides, as the formation of active centres (AC) is not an elementary reaction, b u t a complex process, making it difficult to determine the rate of initiation. Moreover, measurement of the AC concentration in systems of this type has shown that it is considerably lower than the initial catalyst concentration [1, 2]. To discover t h e * Vysokomol. soyed. A17: No. 9, 2059-2062, 1975.
I n i t i a t i o n of t e t r a h y d r o f u r a n p o l y m e r i z a t i o n
2377
reason for the low efficiency of the catalyst system BFs-propylene oxide (PO) in THF polymerization it was desired to make a kinetic investigation of the loss of one of the components of the system, namely PO. PO, BF8 a n d TI-IF were purified b y t h e m e t h o d s described m Ref. [3]. Acetone used as i n t e r n a l s t a n d a r d during separation of the p o l y m e r i z a t i o n s y s t e m was boiled for several periods of 3-4 h r o v e r KMnO4. A c e t o n e was t h e n distilled off o v e r a fresh p o r t i o n of K M n O s , a n d a f r a c t i o n of b.p 56 ° was collected. The p u r i t y of all the reagents was verified b y g.l.c. ("Tsvet-4"). BF8 a n d P O were frozen in s e p a r a t e thin-walled globules which were placed m t h e r e a c t i o n vessel. A f t e r t h e r m o s t a t t m g the globules were broken. T h e p o l y m e r i z a t i o n was carrmd out m t h e m a n n e r described in Ref. [1]. The r e a c t i o n was s t o p p e d b y a solution of t e t r a e t h y l a m m o m u m prorate m TH_F. T h e u n r e a c t e d P O a n d T H F were refrozen m p r e v i o u s l y weighed small flasks to w h i c h a fixed a m o u n t of acet o n e dissolved in T H F was added. T h e resulting m i x t u r e was analysed.
CpO
O0
-f
Oq
12 ^_ SPO
t°~ sAc
Fro. 1 Calibration c u r v e for d e t e r m i n a t i o n of P O concentrations. The m i x t u r e was a n a l y s e d b y g.l.e. ( " T s v e t - 4 " ) using a flame-lomzatlon d e t e c t o r (FID). F r a c t l o n a t l o n of t h e mLxture was effected b y m e a n s of a 2 m long c o l u m n filled w i t h a d l a t o m m earrmr (TND-TS-M) containing h q m d phase (trmthylene glycol, srhcone r u b b e r a n d trmresyl phosphate). T h e carrmr gas was mtrogen. T h e t h e r m o s t a t t e m p e r a t u r e was 62 °, a n d t h a t of t h e e v a p o r a t o r 130 ° U n d e r these conditions t h e r e t e n t i o n t i m e s f o r PO, acetone a n d T H F were respectively 3, 5 and 7.5 m m . Specially p r e p a r e d m i x t u r e s were used for c a h b r a t l o n of t h e eqmpmen~. F o r F I I ) t h e c a h b r a t l o n c u r v e can be rectified satisfactorily on coordinates log CpO/CAc--log Spo/SAc [4]. T h e c a h b r a t l o n c u r v e (Fig. 1) was used to d e t e r m i n e the a m o u n t of P O m a mLxture; K n o w ° m g thin one can d e t e r m i n e t h e a m o u n t of P O r e m a n n n g m the p o l y m e r i z a t i o n s y s t e m . The s e n m t l v l t y of t h e m e t h o d is 10 -4 mole/1, m respect to PO.
After addition of the catalyst system to THF, boron tnfluoride forms complexes with PO and THF. This results in the estabhshment of the equilibrium
;--5A
CH3
) B
CH,
(I)
2378
G.N. KOMRATOVet al.
I n the presence of THF and PO complex B is consumed in the formation of AC CH3 B ,-/-OQ
~.
I + /, BFaOCH=. 1 , --CH--O~
-
CHa
(2)
CHa CH3 [
B ~- 0 C
+
~' ~BFaOCH"---C}I--OC
'
(3)
n~
in view of which the initiation rate constants k, and k,~ will depend both on time for the establishment of an equilibrium, and on the equilibrium constant K for reaction (1). The high reactivity of complex B makes for difficulty in determination of the constants/c 1, k_, and k i / ] c - l = K for the system. To determine K for reaction (1) we used the linear dependence of log K on p K B [5], where K is the constant for the equilibrium between BFaOEt~ and any ether, and p K B characterize the basieity of the latter ether prepared in accordance with O--D chemical shifts of the band in the IR spectrum on mixing CHaOD with the ether . Starting with this dependence and with pKB=6"95 for PO [6] we find that K = 0.4 for the system BFaOEt~-PO. Hence the equilibrium constant for reaction (1) will be 0.016, as K for the system BFaOEt~-TI{F is 25 [7]. Since the equilibrium constant for the system BFaOEt~-PO is close to unity, it is a reasonable assumption that the rate of establishment of equilibrium for (1) will not differ substantially from that for (4) kl'
BY.OEtt_k O C I ~-_1" BFsOC I
+ OEt. ,
(4)
which means that/c-1___/¢-1'> 1051/mole . see [8], and ]¢1~-K.]¢_1~ 10a 1./mole.sec. As the constants kl and k_~ are rather high, it can be said that the equilibrium of (1) is established almost instantaneously. Assuming K to be 0-016, it should be noted that the equilibrium of (1) is displaced maxkedly towards the formation of complex A, although the participation of complex B in reactions (2) and (3) gradually shifts the equilibrium of (1) to the right. The PO present in the system may be consumed not only in reactions (1) and (2), but also as follows:
(5) CHa n,
+0
k' - . n , ,
C6)
Initiation of tetrahydrofuran polymerization
2379
where n 1 and n~ are active centres corresponding to eqns. (2) and (3) respectively. The depletion rate for PO participating in reactions (1), (2), (5) and (6) m a y he expressed as
d [PO] =kl [A] [PO]--k-1 [B] [THF]q-k~ [B] [1)O]-5
dt
(7)
+k3 [PO] [nd+k4 [PO] [n~] On the basis of analysis of the experimental data for T H F polymerization under the action of BF 3 in the presence of ~-oxides under the conditions selected by us ([A]o=10-2; [PO]0=10-2-10-1; [THF]0----12.'~ mole/1 ) we obtain: 1) In1]<< <<[ns], and [n2]<[A]0 111 accordance with Ref [l]; 2)[B]0_~K[A]°[P~u]°~10 -6 [THF]o mole/1 in accordance with eqn (1) This means that all the quantities on the right-hand side of eqn. (7) m a y be neglected, with the exception of the first and second, whereupon the depletion rate for PO may be written as d [PO] --kl [h] [PO]--k_~ [B] [THF], dt
(8)
and the rate of change m the concentration of complex B
g [B] dt
k I [A] [PO]--L~ [B] [THF]--k, [B] [THF]
(9)
Using the method of stationary concentrations, we obtain an expression for the concentration of complex B [B]=
k~ [A] [PO] k_l [THF]--k, [THF]
(10)
Substituting expression (10) into (8), we obtain
d [PO]
at
k~ [A] [PO]--
k_ ~kl [A] [PO]
k_1--k~
(11)
and after rearrangement we have d [PO] dt
klk 3
= k ~ k ~ [A] [PO]
(12)
By integration of (12) we obtain an expresion giving the PO concentration [PO] =
[POlo ([A]o--[PO]o)
[klk~ [A]o cxp L~-~J ([A]o-- [POlo) t]-- [POlo
(13)
It appears t h a t the relatmns of In [PO] to t will not be hnear. Figure 2 shows the kinetic curves for PO depletion in relation to initial PO concentration in the polymerization system. Satisfactory rectification of these
2380
G. lq. KOMa~TOV et al
curves is obtained on In PO-time coordinates (Fig. 3), in accordance with the eqn. (14) In [PO] = l n [PO]0--Kk ~[A]. t,
(14)
which one obtains on integrating eqn. (12), assuming that [A] is constant and equal to [A]o. It is seen from Fig. 3, showing plots of PO vs. time, that for ratios of [PO]0 : [BFs]0=I, 2 and 5 the tangent of the angle of slope of the curves is identical and equal to (0.854-0.05)× 10 -3 sec -~, and for the ratio [PO]0 : [BFs]o
[p0],10,%oJs/z 8
lo~[Po~ -10
z,
8 2
/
~
o
-2 0 ~
_
-30~ -¢0
10
30 Tzme , mzn
FIG. 2
3
50
I lO
I
0 I 30 Tzme ~rain
I
I 50
FIG. 3
FIo. 2. Kmetm curves for PO depletion relative to mltial PO concentration m the polymerization system. Mass polymerization at 20° with [BF,]0----9.3 × 10 -s mole/l. [PO]0 • [BFsl, ----10 (1), 5 (2), 2 (3) and (d). FIG. 3. Seml-logarlthmm anamorphoses of the kinetm curves for PO depletion seen in Fig. 2. : 10-0.63 ><10 -a sec -1. This is apparently due to the fact that up to [PO]o : [BFa]o ----5 the amount of AC formed in the system is insignificant compared with BF 8 owing to deactivation, which is probably accompanied by the regeneration of BF3, so t h a t the main portion of BF a is in the form of complex A, so that within the period of time examined one m a y regard [A] as being constant and equal to [BFa]0. On the other hand in the case of [PO]0 : [BF3]0----10 A is constant, but lower than [BFa]0 on account of the formation of a larger amount of AC, which is reflected in change in the slope of the In [PO] vs. t plot. Given the slope of the curves m Fig. 3 and the initial concentration [A]0 it was found by calculation that K.k~ 0.0904,0.005 1./mole.sec, using eqn. (14). Knowing that K----0.016 one finds that the rate of imtlation k~----5.5 1./mole.sec. F r o m these results and from an analysis of possible directions of PC depletion it appears that PO participates mainly in the initiation process m the form of complex B. The formation of AC takes place through interaction of T H F with the latter complex, the concentration of which is extremely low (owing to the low concentration of PO compared with T H F and the very low value of K). The initiation rate is therefore commensurate with the rate of chain propaga-
Melting of polywnylideno fluoride
2381
tion, as was prevmnsly proposed in Re£ [3]. I t should be noted t h a t as the equihbrium constant K for B F s . O C [ . ~ cyclic ether [5, 7] varies with the use of different cyclic ethers as eocatalysts, it would seem that there are bound to be changes in the initiation rates as well. Translated by R . ft. A. HEYDAY REFERENCES 1. R. A. BARZYKINA, G. N. KOMRATOV, G. V. KOROVINA and S. G. ENTELIS, Vysokernel, soyed. A16: 906, 1974 (Translated in Polymer Sel. U S S.R. 16: 4, 1048, 1970) 2. T. SAEGUSA and S. MATSUMOTO, Macromoleeules 1: 442, 1968 3. R. A. BARZYKINA, G. V. KOROVINA, O. M. OL'KHOVA, Ya. I. YESTRIN and S. G. ENTELIS, Vysokomol. soyed. A10: 315, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 2, 369, 1968) 4. A. F. NIKOLAYEV, K. V. BELOGORODSKAYA, A. I. ANDREYEV and V. G. RUMYANTSEV, Vysokomol. soyed. A15: 436, 1973 (Translated in Polymer ScL U.S.S.R. 15: 2, 495, 1973) 5. M. OKADA, K. SUGAMA and J. JAMASHITA, Totrahodron Letters 28: 2329, 1965 6. S. IWATSUKI, N. T A K I K k W A , M. OKADA and J. JAMASHITA, Polymer Letters 2: 549, 1964 7. I. S. MOROZOVA, L. A. KHARITONOVA, B. L. RYTOV, M. A. MARKEVICH, G. V. RAKOVA and N. S. YENIKOLOPYAN, Dokl. A_~ SSSR 212: 146, 1973 8. A. S. RUTENBERG and A. A. PALKO, J. Phys. Chem. 69: 527, 1965
THE EFFECT OF CRYSTALLINE MODIFICATIONS ON THE. MELTING OF POLYVINYLIBENE FLUORIDE* G M BARTEI~EV, A . A. REMIZOVA, I . V. KULESHOV, ~/[. A. ~A_~Tr~OV a n d T. 1~. SARMI~SKAYA Phymeal Chemistry Institute, U S.S.R. Academy of Semneos V. I. Lenin State Pdagogaeal Institute, Moscow " P l a s t p o l y m e r " Industrial Research Association (Reee,ved 8 August 1974) The melting of different crystalline modifications of polyvmyhdene fluomdo (PVDF) was investigated b y the X - r a y method and b y volume dflatometrm analyms. The melting of low pressure y-phase (200 arm) was m v e s h g a t e d for the first time. The measurements were earrmd out over the temperature range 20-250 °. I t was found t h a t the melting point of P V D F is determined b y at least two factors: 1) the erystalhne modlficahon of the polymer, the propertms of whmh are m turn determined b y t h e * Vysokomol. soyed A17: No 9, 2063-2068, 1975.
G . N . KO~RATOV et aL
5. N, N. MAKAROVA, Dissertation, 1971 6. V. S. PAPKOV and G. I,. SLONIMSKII, Vysokomol soyed. 8: 80, 1966 (Translated in Polymer Sei. U.S.S R 8: 1, 84, 1966) 7. S. N. ZHURKOV and E. Ye. TOMASHEVSKII, Sb. Nekotorye problemy prochnosti tverdogo tela (Some Problems of the Strength of Sohd Substances). I z d A N SSSR, 1959 8. Yu. P. KVACHEV, V. S. PAPKOV, V. Yu. LEVIN, A. A. ZHDANOV, G. L. SLONIMSgll and K. A. ANDRIANOV, Dokl A N SSSR 215: 4073, 1974 9. K. A. ANDRIANOV, G. L. SLONIMSKII, D. Ya. TSVANKIN, V. S. PAPKOV, V. Yu. LEVIN, Yu. P. KVACHEV, M. N. ILYINA and N. N. MAKAROVA, Vysokomol. soyed. B16: 208, 1974 (Not translated in Polymer Scl. U.S.S R ) 10. Yu. P. KVACHEV, I. I. PEREPECHKO, V. S. PAPKOV, V. Yu. LEVIN, A. A. ZHDANOV, G. L. SLONIMSKII and K. A. ANDRIANOV, Mekhamka pohmerov, 804, 1973 l l . C. L. FRYE and J. M. KLOSOWSKI, J. Amer. Chem. Soc 93: 4599, 1971
KINETIC INVESTIGATION OF THE INITIATION OF TETRAHYDROFURAN POLYMERIZATION BY THE SYSTEM BFs-PROPYLENE OXIDE* G. N. KOMRATOV, R. A. :BARzYKI~A, G V. KOROVI~A and S. G. EI~TELI8 Chenncal Physics Institute, U.S.S.R. A c a d e m y of Scmnces (Recewed 7 August 1974)
A kmetm s t u d y was made of changes in the concentration of propylene oxldo m the polymerLzatlon of tetrahydrofuran initiated b y the system BFa-propylene oxide, using the g.l.e, method. Tt m shown t h a t consumption of the ~-oxlde proceeds in accordance with a first order law. This is a p p a r e n t l y due to the effect of reactions of lmaltatlon of chain growth, whmh are aecompamed b y the regeneration of BF3. Within the period of time examined the BF8 concentratmn m a y therefore be taken to be constant and equal to [BFs]0. The rate of lmtlatmn was determmed (k~--~5 5 L/mole. see).
VERY little study has been made of the imtiation stage m the polymerization o f tetrahydrofuran (THF) under the action of B F 3 in the presence of e-oxides, as the formation of active centres (AC) is not an elementary reaction, b u t a complex process, making it difficult to determine the rate of initiation. Moreover, measurement of the AC concentration in systems of this type has shown that it is considerably lower than the initial catalyst concentration [1, 2]. To discover t h e * Vysokomol. soyed. A17: No. 9, 2059-2062, 1975.
I n i t i a t i o n of t e t r a h y d r o f u r a n p o l y m e r i z a t i o n
2377
reason for the low efficiency of the catalyst system BFs-propylene oxide (PO) in THF polymerization it was desired to make a kinetic investigation of the loss of one of the components of the system, namely PO. PO, BF8 a n d TI-IF were purified b y t h e m e t h o d s described m Ref. [3]. Acetone used as i n t e r n a l s t a n d a r d during separation of the p o l y m e r i z a t i o n s y s t e m was boiled for several periods of 3-4 h r o v e r KMnO4. A c e t o n e was t h e n distilled off o v e r a fresh p o r t i o n of K M n O s , a n d a f r a c t i o n of b.p 56 ° was collected. The p u r i t y of all the reagents was verified b y g.l.c. ("Tsvet-4"). BF8 a n d P O were frozen in s e p a r a t e thin-walled globules which were placed m t h e r e a c t i o n vessel. A f t e r t h e r m o s t a t t m g the globules were broken. T h e p o l y m e r i z a t i o n was carrmd out m t h e m a n n e r described in Ref. [1]. The r e a c t i o n was s t o p p e d b y a solution of t e t r a e t h y l a m m o m u m prorate m TH_F. T h e u n r e a c t e d P O a n d T H F were refrozen m p r e v i o u s l y weighed small flasks to w h i c h a fixed a m o u n t of acet o n e dissolved in T H F was added. T h e resulting m i x t u r e was analysed.
CpO
O0
-f
Oq
12 ^_ SPO
t°~ sAc
Fro. 1 Calibration c u r v e for d e t e r m i n a t i o n of P O concentrations. The m i x t u r e was a n a l y s e d b y g.l.e. ( " T s v e t - 4 " ) using a flame-lomzatlon d e t e c t o r (FID). F r a c t l o n a t l o n of t h e mLxture was effected b y m e a n s of a 2 m long c o l u m n filled w i t h a d l a t o m m earrmr (TND-TS-M) containing h q m d phase (trmthylene glycol, srhcone r u b b e r a n d trmresyl phosphate). T h e carrmr gas was mtrogen. T h e t h e r m o s t a t t e m p e r a t u r e was 62 °, a n d t h a t of t h e e v a p o r a t o r 130 ° U n d e r these conditions t h e r e t e n t i o n t i m e s f o r PO, acetone a n d T H F were respectively 3, 5 and 7.5 m m . Specially p r e p a r e d m i x t u r e s were used for c a h b r a t l o n of t h e eqmpmen~. F o r F I I ) t h e c a h b r a t l o n c u r v e can be rectified satisfactorily on coordinates log CpO/CAc--log Spo/SAc [4]. T h e c a h b r a t l o n c u r v e (Fig. 1) was used to d e t e r m i n e the a m o u n t of P O m a mLxture; K n o w ° m g thin one can d e t e r m i n e t h e a m o u n t of P O r e m a n n n g m the p o l y m e r i z a t i o n s y s t e m . The s e n m t l v l t y of t h e m e t h o d is 10 -4 mole/1, m respect to PO.
After addition of the catalyst system to THF, boron tnfluoride forms complexes with PO and THF. This results in the estabhshment of the equilibrium
;--5A
CH3
) B
CH,
(I)
2378
G.N. KOMRATOVet al.
I n the presence of THF and PO complex B is consumed in the formation of AC CH3 B ,-/-OQ
~.
I + /, BFaOCH=. 1 , --CH--O~
-
CHa
(2)
CHa CH3 [
B ~- 0 C
+
~' ~BFaOCH"---C}I--OC
'
(3)
n~
in view of which the initiation rate constants k, and k,~ will depend both on time for the establishment of an equilibrium, and on the equilibrium constant K for reaction (1). The high reactivity of complex B makes for difficulty in determination of the constants/c 1, k_, and k i / ] c - l = K for the system. To determine K for reaction (1) we used the linear dependence of log K on p K B [5], where K is the constant for the equilibrium between BFaOEt~ and any ether, and p K B characterize the basieity of the latter ether prepared in accordance with O--D chemical shifts of the band in the IR spectrum on mixing CHaOD with the ether . Starting with this dependence and with pKB=6"95 for PO [6] we find that K = 0.4 for the system BFaOEt~-PO. Hence the equilibrium constant for reaction (1) will be 0.016, as K for the system BFaOEt~-TI{F is 25 [7]. Since the equilibrium constant for the system BFaOEt~-PO is close to unity, it is a reasonable assumption that the rate of establishment of equilibrium for (1) will not differ substantially from that for (4) kl'
BY.OEtt_k O C I ~-_1" BFsOC I
+ OEt. ,
(4)
which means that/c-1___/¢-1'> 1051/mole . see [8], and ]¢1~-K.]¢_1~ 10a 1./mole.sec. As the constants kl and k_~ are rather high, it can be said that the equilibrium of (1) is established almost instantaneously. Assuming K to be 0-016, it should be noted that the equilibrium of (1) is displaced maxkedly towards the formation of complex A, although the participation of complex B in reactions (2) and (3) gradually shifts the equilibrium of (1) to the right. The PO present in the system may be consumed not only in reactions (1) and (2), but also as follows:
(5) CHa n,
+0
k' - . n , ,
C6)
Initiation of tetrahydrofuran polymerization
2379
where n 1 and n~ are active centres corresponding to eqns. (2) and (3) respectively. The depletion rate for PO participating in reactions (1), (2), (5) and (6) m a y he expressed as
d [PO] =kl [A] [PO]--k-1 [B] [THF]q-k~ [B] [1)O]-5
dt
(7)
+k3 [PO] [nd+k4 [PO] [n~] On the basis of analysis of the experimental data for T H F polymerization under the action of BF 3 in the presence of ~-oxides under the conditions selected by us ([A]o=10-2; [PO]0=10-2-10-1; [THF]0----12.'~ mole/1 ) we obtain: 1) In1]<< <<[ns], and [n2]<[A]0 111 accordance with Ref [l]; 2)[B]0_~K[A]°[P~u]°~10 -6 [THF]o mole/1 in accordance with eqn (1) This means that all the quantities on the right-hand side of eqn. (7) m a y be neglected, with the exception of the first and second, whereupon the depletion rate for PO may be written as d [PO] --kl [h] [PO]--k_~ [B] [THF], dt
(8)
and the rate of change m the concentration of complex B
g [B] dt
k I [A] [PO]--L~ [B] [THF]--k, [B] [THF]
(9)
Using the method of stationary concentrations, we obtain an expression for the concentration of complex B [B]=
k~ [A] [PO] k_l [THF]--k, [THF]
(10)
Substituting expression (10) into (8), we obtain
d [PO]
at
k~ [A] [PO]--
k_ ~kl [A] [PO]
k_1--k~
(11)
and after rearrangement we have d [PO] dt
klk 3
= k ~ k ~ [A] [PO]
(12)
By integration of (12) we obtain an expresion giving the PO concentration [PO] =
[POlo ([A]o--[PO]o)
[klk~ [A]o cxp L~-~J ([A]o-- [POlo) t]-- [POlo
(13)
It appears t h a t the relatmns of In [PO] to t will not be hnear. Figure 2 shows the kinetic curves for PO depletion in relation to initial PO concentration in the polymerization system. Satisfactory rectification of these
2380
G. lq. KOMa~TOV et al
curves is obtained on In PO-time coordinates (Fig. 3), in accordance with the eqn. (14) In [PO] = l n [PO]0--Kk ~[A]. t,
(14)
which one obtains on integrating eqn. (12), assuming that [A] is constant and equal to [A]o. It is seen from Fig. 3, showing plots of PO vs. time, that for ratios of [PO]0 : [BFs]0=I, 2 and 5 the tangent of the angle of slope of the curves is identical and equal to (0.854-0.05)× 10 -3 sec -~, and for the ratio [PO]0 : [BFs]o
[p0],10,%oJs/z 8
lo~[Po~ -10
z,
8 2
/
~
o
-2 0 ~
_
-30~ -¢0
10
30 Tzme , mzn
FIG. 2
3
50
I lO
I
0 I 30 Tzme ~rain
I
I 50
FIG. 3
FIo. 2. Kmetm curves for PO depletion relative to mltial PO concentration m the polymerization system. Mass polymerization at 20° with [BF,]0----9.3 × 10 -s mole/l. [PO]0 • [BFsl, ----10 (1), 5 (2), 2 (3) and (d). FIG. 3. Seml-logarlthmm anamorphoses of the kinetm curves for PO depletion seen in Fig. 2. : 10-0.63 ><10 -a sec -1. This is apparently due to the fact that up to [PO]o : [BFa]o ----5 the amount of AC formed in the system is insignificant compared with BF 8 owing to deactivation, which is probably accompanied by the regeneration of BF3, so t h a t the main portion of BF a is in the form of complex A, so that within the period of time examined one m a y regard [A] as being constant and equal to [BFa]0. On the other hand in the case of [PO]0 : [BF3]0----10 A is constant, but lower than [BFa]0 on account of the formation of a larger amount of AC, which is reflected in change in the slope of the In [PO] vs. t plot. Given the slope of the curves m Fig. 3 and the initial concentration [A]0 it was found by calculation that K.k~ 0.0904,0.005 1./mole.sec, using eqn. (14). Knowing that K----0.016 one finds that the rate of imtlation k~----5.5 1./mole.sec. F r o m these results and from an analysis of possible directions of PC depletion it appears that PO participates mainly in the initiation process m the form of complex B. The formation of AC takes place through interaction of T H F with the latter complex, the concentration of which is extremely low (owing to the low concentration of PO compared with T H F and the very low value of K). The initiation rate is therefore commensurate with the rate of chain propaga-
Melting of polywnylideno fluoride
2381
tion, as was prevmnsly proposed in Re£ [3]. I t should be noted t h a t as the equihbrium constant K for B F s . O C [ . ~ cyclic ether [5, 7] varies with the use of different cyclic ethers as eocatalysts, it would seem that there are bound to be changes in the initiation rates as well. Translated by R . ft. A. HEYDAY REFERENCES 1. R. A. BARZYKINA, G. N. KOMRATOV, G. V. KOROVINA and S. G. ENTELIS, Vysokernel, soyed. A16: 906, 1974 (Translated in Polymer Sel. U S S.R. 16: 4, 1048, 1970) 2. T. SAEGUSA and S. MATSUMOTO, Macromoleeules 1: 442, 1968 3. R. A. BARZYKINA, G. V. KOROVINA, O. M. OL'KHOVA, Ya. I. YESTRIN and S. G. ENTELIS, Vysokomol. soyed. A10: 315, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 2, 369, 1968) 4. A. F. NIKOLAYEV, K. V. BELOGORODSKAYA, A. I. ANDREYEV and V. G. RUMYANTSEV, Vysokomol. soyed. A15: 436, 1973 (Translated in Polymer ScL U.S.S.R. 15: 2, 495, 1973) 5. M. OKADA, K. SUGAMA and J. JAMASHITA, Totrahodron Letters 28: 2329, 1965 6. S. IWATSUKI, N. T A K I K k W A , M. OKADA and J. JAMASHITA, Polymer Letters 2: 549, 1964 7. I. S. MOROZOVA, L. A. KHARITONOVA, B. L. RYTOV, M. A. MARKEVICH, G. V. RAKOVA and N. S. YENIKOLOPYAN, Dokl. A_~ SSSR 212: 146, 1973 8. A. S. RUTENBERG and A. A. PALKO, J. Phys. Chem. 69: 527, 1965
THE EFFECT OF CRYSTALLINE MODIFICATIONS ON THE. MELTING OF POLYVINYLIBENE FLUORIDE* G M BARTEI~EV, A . A. REMIZOVA, I . V. KULESHOV, ~/[. A. ~A_~Tr~OV a n d T. 1~. SARMI~SKAYA Phymeal Chemistry Institute, U S.S.R. Academy of Semneos V. I. Lenin State Pdagogaeal Institute, Moscow " P l a s t p o l y m e r " Industrial Research Association (Reee,ved 8 August 1974) The melting of different crystalline modifications of polyvmyhdene fluomdo (PVDF) was investigated b y the X - r a y method and b y volume dflatometrm analyms. The melting of low pressure y-phase (200 arm) was m v e s h g a t e d for the first time. The measurements were earrmd out over the temperature range 20-250 °. I t was found t h a t the melting point of P V D F is determined b y at least two factors: 1) the erystalhne modlficahon of the polymer, the propertms of whmh are m turn determined b y t h e * Vysokomol. soyed A17: No 9, 2063-2068, 1975.