- Email: [email protected]
The effect of plasticization on the dielectric relaxation of polymethylmethacrylate
1294
A.M. LOB~NOVet al. REFERENCES
1. L. KLEINER, Plastv~rlden 5: 205, 1955 2. I. M. AL'SHITS, Poliefirnye stekloplastiki dlya sudostroyeniya (Polyester GRPs for Ship-building). Izd. "Sudostroyenie", 1964 3. A. M. KHAIKIN and Kh. A. PARKSHEYAN, Plast. massy, No. 10, 40, 1965 4. V. V. KORSHAK, T. A. SIDOROV, S. V. VINOGRADOVA, L. I. KOMAROVA, P. M. VALETSKII and A. S. LEBEDEVA, Izv. AN SSSR, Chem. series, 261, 1965 5. V. V. KORSHAK, S. V. VINOGRADOVA and A. S. LEBEDEVA, U.S.S.R. Pat. No. 134857, 1960; Byull. izob., No. 1, 1961 6. A. CONIX, Ind. Chim. Belge 22: 1457, 1957 7. V. V. KORSHAK and S. V. VINOGRADOVA, Poliarylaty (Polyarylates). Izd. "Nauka", 1964 8. F. R. MAYO and M. LEWIS, J. Amer. Chem. Soc. 66: 1694, 1944 9. T. ALFREY, D. BORRER and G. MARK, Copolymerization, Foreign Lit. Pub. House, 1953 10. A. V. TOKAREV, Thesis, 1959
THE
EFFECT
OF
RELAXATION
PLASTICIZATION
ON
THE
DIELECTRIC
OF P O L Y M E T H Y L M E T H A C R Y L A T E *
A. M. LOBANOV, D. M. MIRKAMILOV and M. P. PLATO~OV High Molecular Weight Compounds Institute, U.S.S.R. Academy of Sciences (Received 3 J u n e 1967)
IN A n u m b e r of papers [1-4] it was shown t h a t the m o s t probable r e l a x a t i o n time a n d the a c t i v a t i o n e n e r g y of the dipole-group (dipole-radical) process o f polar polymers (polyvinylchloride, p o l y m e t h y l a c r y l a t e , p o l y v i n y l b u t y r a l , polyv i n y l a c e t a t e ) are altered b y the i n t r o d u c t i o n of plasticizers. The most p r o b a b l e r e l a x a t i o n time of the p o l y m e r m a y be d e t e r m i n e d b o t h t h r o u g h t h e intramolecular and also t h r o u g h the interchain interaction. The effect of plasticization on the most probable r e l a x a t i o n time of the dipole-group process indicates t h a t this process depends on the m a g n i t u d e of the interchain interaction which is weakened b y introducing a plasticizer. I t was shown in [5] t h a t when d i b u t y l p h t h a l a t e (DBP) is t h e plasticizer i n t r o d u c e d into p o l y m e t h y l m e t h a c r y l a t e (PMMA) the most p r o b a b l e r e l a x a t i o n time of the dipole-segmental (dipole-elastic) process is reduced, while the m o s t probable relaxation time of the dipole-group process remains constant. Moreover the dielectric losses for the dipole-group process also r e m a i n c o n s t a n t in the region of the m a x i m u m . * Vysokomol. soyed. A10: No. 5, 1116-1121, 1968.
Effect of plasticization on dielectric relaxation of polymethylmethacrylate
1295
On t h e o t h e r h a n d t h e r e is no dielectric dispersion for P M M A soIutions [6-8] in t h e t e m p e r a t u r e a n d f r e q u e n c y region where t h e dipole-group process d e v e l o p s for b u l k PMMA. I n a s t u d y of P M M A plasticized w i t h toluene [7] a t frequencies of 400 c/s a n d a b o v e (i.e. a t frequencies for which t h e r e will be only one region of t a n 5 ~ on a c c o u n t of t h e dipole-group a n d d i p o l e - s e g m e n t a l processes being c o m b i n e d ) it was also s h o w n t h a t as t h e c o n c e n t r a t i o n of t h e plasticizer (toluene) in P M M A increases t h e c o m b i n e d v a l u e o f t a n 5max is displaced into t h e lower t e m p e r a t u r e region, i.e. t h e r e l a x a t i o n t i m e for the c o m b i n e d process is reduced. I n view of t h e a b o v e e x p e r i m e n t a l results it is h a r d to r e a c h a n y definite conclusion r e g a r d i n g t h e effect of p l a s t i c i z a t i o n on t h e dipole-group processes in PMMA. This p a p e r is a s t u d y o f t h e effect of plasticizers on b o t h r e l a x a t i o n processes in PMMA. T h e m e a s u r e m e n t s were car led out a t low frequencies w h e r e t h e " r e s o l u t i o n " of b o t h regions of t h e r e l a x a t i o n process is good.
EXPERIMENTAL The PMMA used for the experiments was obtained by radical polymerization (11//w ~70,000). By repreeipitation in hexane from a solution of the polymer in benzene low molecular weight impurities were removed from the samples, which were dried at 90 ° under a pressure of 10 -2 mmI-Ig. The samples used for the measurements were prepared in film form, the solvent being slowly evaporated from a 20% PMMA solution in toluene. The bottom of the light nickel cup containing the solution to be evaporated served as the lower electrode. The upper electrode was made from aluminium foil while the sample was being prepared. The amount of toluene in the sample was checked after the measurements while the sample was being dried to constant weight. DBP was introduced to PMMA by mechanical mixing in an agate mortar. Samples were press-moulded from a freshly prepared mixture at 150 ° in the form of discs 25-30 mm in dia. and approximately 100-130/l thick. A low-frequency bridge was used for the measurements at frequencies of 1, 5.5, 20 and 70 c/s over the range --60 to 140 °. (The bridge was developed by A. I. Artyuskhov and D. A. Dmitrochenko at the High Molecular Weight Compounds Institute of the U.S.S.R. Academy of Sciences, and was described in [9, 10]. DISCUSSION OF RESULTS
F i g u r e 1 shows t h e results o b t a i n e d b y m e a s u r i n g t a n 5 for P M M A a n d for P M M A plasticized w i t h toluene. I t will be seen t h a t all t h e s a m p l e s o v e r t h e t e m p e r a t u r e i n v e s t i g a t e d h a v e a well defined region o f t a n ~=~x for d i p o l e - s e g m e n t a l a n d d i p o l e - g r o u p processes. T h e region o f t a n ~ a x for b o t h processes is displaced into t h e lower t e m p e r a t u r e region as t h e toluene c o n t e n t of t h e p o l y m e r increases. W h e n the c o n t e n t of toluene in t h e P M M A is increased to 1 3 % t a n 5rex for t h e dipole-group process rises, b u t is r e d u c e d b y f u r t h e r increase ( 2 0 - 3 0 0 ) in t h e toluene content. T h e v a l u e of t a n 5m~x for the d i p o l e - s e g m e n t a l process increases w i t h increase in t h e toluene c o n t e n t o f the PMMA. F i g u r e l a also shows t h a t t h e a d d i t i o n o f toluene to t h e P M M A results in a rel a t i v e l y large d i s p l a c e m e n t of t h e r e g i o n of t a n 5~a~ for t h e d i p o l e - s e g m e n t a l
1296
A , M. LOBANOVet al.
tanO,10 2
J
-50
-~0
-ZO
0
20
~0
GO
80
I
fO0
l
/20
7:. o C
tan, I, lO~
5
,~
I
-#0
-ItO
I
-20
I
0
20
r
40
I
60
,,J
80
I
I
~00
120
140
FIG. I. Tan 6 plotte~[against temperatuxe for samples of P M M _ ~ plasticized~ t h ~oluene at frequencies of 1 (a) and 5.5 c/s (b): 1--0, 2--6.5, 3--13, 4--20 ~ d ~--31% (by wt.) toluene.
Effect of plasticization on dielectric relaxation of polymethylmethaerylate
1297
process compared with the dipole-group process. For example, the addition of 6.5% of toluene displaces the region of tan ~max for the dipole-segmental process b y 36 ° in the lower temperatures direction, b u t b y only 3 ° in the same direction with respect to the dipole-group process. The two processes are therefore combined in the case of certain toluene concentrations. The combination of both processes and the appearance of a single asymmetrical maximum for tan g as the toluene content of the PMMA increases is clearly revealed at a frequency of 5.5 c/s. Figure lb shows that increase in the amount of toluene in the PMMA displaces the combined process into the lower temperature region, and this agrees with the results obtuined in [7]. With a rise in the frequency of the electric field the tan 5 maximum appears at higher temperatures, and the curve becomes les~ asymmetrical. Similar results were obtained for the plasticization of PMMA with the polar plasticizer DBP. Figure 2 shows the curves of tan 5 vs. temperature for plasticized and unplasticized PMMA. It is apparent that with increase in the percentage content of D B P in PM~IA the position of the region of the maximum for the dipolesegmental and dipole-group processes is displaced into the lower temperature region At the same time the value of tan gmax for both dipole-segmental and dipole-group processes increases with a rise in the percentage content of D B P in PMMA. At higher temperatures there is a rise in tan g due to increased electrical conductivity, on account of which the region of tan 5~ax for the dipole-segmental process is smoothed out, and in the case of curve 4 in Fig. 2 does not appear. Figure 3 shows the temperature position of the region of tan 5max for the dipolesegmental (Tmax d.~.) and dipole group (Tmax d.~.) processes plotted against percentage content of toluene and DBP. Figure 3a shows that Tmax d.s. decreases linearly with increase in the percentage content of plasticizer in PMMA. In view of the linear relation of Tmax d.s. tO concentration and also the fact that PMMA is soluble in toluene and D B P it may be concluded that molecular (intrabundle) plasticization [11] takes place in the systems investigated. There is a nonlinear change in Tmax d.g. (Fig. 3b) as the percentage content of plasticizer in the polymer increases. The most marked change in Tmax d.g. occurs with plasticizer concentrations exceeding 10~o. With quite small amounts of plasticizer in PMMA (up to 5-7%) there is only slight change in Tm~x d.g.- Because of this the independence of the temperature position of the region of tan 5max for the dipole-group (dipole-radical) process in relation to the amount of D B P added, which was noted in [5], is due to the small amount of D B P introduced. The rise in tan g~= for both processes with plasticization m a y be due to dipolegroup and dipole-segmental processes being superimposed on one another. The reduction in tan fi~- for the dipole-group process when the PMMA contaifis a certain amount of toluene (Fig. la) is probably due to decrease in the number of polar groups per unit volume of polymer. Displacement of the region of tan g~x for the dipole-segmental process into
1298
A . M . LoBA~ov et al.
the lower temperature region indicates reduction in relaxation time. This is apparently due to the fact that plasticizer molecules reacting with polymer molecules destroy the interchain bonds that had previously existed, and reduce the interchain interaction. The weakening of interchain interaction increases the mobility of the chain segments, and this is reflected in the shorter relaxation time. The absence of change in the most probable relaxation time for the dipolegroup process if small amounts of plasticizer (up to 7%) are added shows t h a t localization plays a greater.part in the dipole-group than in the dipole segmental process. The authors of [5] point out that in PMMA the dipole-group process II ° is due to reorientation of the O = C - - O - - C H a polar group with a small segment of the main carbon chain. With further increase in the plasticizer content the region of tan 5ma* for the dipole-group process is shifted in the direction of lower temperatures, i.e. just as in the case of the dipole-segmental process the relaxation time is reduced. This m a y be connected with increased mobility of the kinetic groups responsible for dipole-group losses, as a result of the reduced interchain
;~an/~28,f0
,l
2 J S !
-40
-ZL7
L7
ZO
40
C0
80
fog
/ZO ~°C
FIG. 2. Tan • plotted against temperature for PMMA samples plasticized with DBP, a t a frequency of 1 e]s: 1--0, 2--7.5, 3--15 and 4--20~o (by wt.) DBP.
Effect of plasticization on dielectric relaxation of polymethylmethacrylate
1299
Tmaxd, ,°C
-wi
b
10
, 20
5
(
,
30' 0 10 Plasticizer, %
,
20
30
FIG. 3. Temperature position of the region of the maximum for dipole-segmental (Tmax d.s.) (a) and dipole-group (Tmaxa.g.) (b) processes plotted against percentage content of toluene (1), DBP (2) ha polymer. Frequency 1 c/s. interaction. This assumption is supported by experimental results regarding the effect of pressure on this process in PMMA [12], and the effect of plasticization on the process of mechanical relaxation [ 13] which occurs with PMMA in the glasslike state, and which is the analogue of the dipole-group process. Thus both the dipole-segmental process and also the dipole-group process depend on the magnitude of interchain interaction. In conclusion we would point out t h a t irrespective of whether the polar group is rigidly attached to the main chain (polyvinylchloride, polyvinylbutyral), or whether internal rotation of the polar group is possible (polymethacrylate, polymethylmethacrylate, polyvinylacetate), the introduction of plasticizer affects the most probable relaxation time of the dipole-group process. CONCLUSIONS
(1) I t has been established t h a t in the plasticization of polymethylmethacrylate by polar and nonpolar plasticizers the relaxation time for the dipole-group and dipole-segmental processes is reduced. (2) The mobility of kinetic groups which are responsible for both the dipolesegmental and also the dipole-group losses depends on the interchain interaction. Translated by R. ft. A. ~IENI)R¥ REFERENCES
1. G. P. MIKkIAII,0V, A. M. LOBANOV and D. M. MIRKAMILOV, Vysokomol. soyed. 8: 1351, 1966 (Translated in Polymer Sei. U.S.S.R. 8: 8, 1483, 1967) 2. G. P. MIK~J.L0V, A. M. LOBANOV and D. M. MIRKAM~L0V, Vysokomol. soyed. A10: 826, 1968 (Translated ha Polymer Sci, U.S.S.R. AID: 4,959, 1968) 3. G. P. M I ~ O V , T. I. BORISOVA and A. 8. NIGMANKHODZHAYEV, Vysokomol. soyed. 9: 991, 1966 (Translated in Polymer Sci. U.S.S.R. 8: 6, 1088, 1966)
1300
Yu. N, SAZANOVet al.
4. P. F. VESELOVSKII and I. A. GANDEL'MAN, Radioelectronika, Trans. Leningrad Polytech. Institute, No. 255, 148, 1965 5. G. P. MIKHAILOV, T. I. BORISOVA and D. A. DMITROCHENKO, Zh. tekhn, fiz. 26: 1924, 1956 6. L. de BROUSKERE, D. BUESS, I. de BOCK and I. VERSLUYS, Bull. Soe. Chim. Belges 64: 669, 1955 7. P. F. VESELOVSKII and V. K. MATVEYEV, Vysokomol. soyed. 6: 1221, 1964 (Translated in Polymer Sci. U.S.S.R. 6: 7, 1345, 1964) 8. G. P. I~[~IAILOV, A. M. LOBANOV and M. P. PLATONOV, Vysokomol. soyed. 8: 692, 1966 (Translated in Polymer Sci. U.S.S.R. 8: 4, 760, 1966) 9. T. NAKAJIMA and D. KONDO, Bull. Electroteehn. Lab. 20: 641, 1956 10. E. SCI~OSSER and G. HORN, Experimentelle Teehnik der Physik. XI: No. 2, 145, 1963 11. P. V. KOZLOV, ZhVKhO ira. Mendeleyeva 9: 660, 1964 12. I. KOPPELMAN and J. GIELESSEN, Kolloid-Z. 175: 97, 1961 13. E. IENKEL and K. ILLERS, Z. Naturforsch., B, A9: No. 5, 440, 1954
POLYMERIZATION OFp,p-bis-CHLOROMETHYL-fl-PROPIOLACTONE Y r . N. SAZA~OV, N. A. GLUK~OV and M. M. KOTO~ High Molecular Weight Compounds Institute, U.S.S.R. Academy of Sciences
(Received 3 July 1967)
I x A previous paper it was shown that the use of fl-lactones as monomers with substituents at the fl-carbon atom is of interest to authors because the synthesis of these monomers presents no difficulties. These lactones are usually produced in a single stage process b y the condensation of ketene with the appropriate earbonyl compounds. I t was shown in [1] following a study of the polymerization of fl,fl-dimethyl-fl-propiolactono that the latter polymerizes very slowly within a very narrow temperature range, and provides relatively low molecular weight compounds; this low activity m a y be the result of the inductive effect of the two methyl groups at the fl-carbon atom reinforcing the alkyl-oxygen bond of the lactone ring, i.e. the bond which opens and causes polymerization of the lactone. In order to weaken the alkyl-oxygen bond electron-acceptor substituents must be i n t r o d u c e d a t t h e f l - c a r b o n a t o m ; e h l o r o m e t h y l g r o u p s w e r e s e l e c t e d as t h e s e s u b s t i t u e n t s , a n d fl,fl-bis-chloromethyl-fl-propiolactone (fl-BCML) w a s s y n t h e s i z e d a n d t h e n p o l y m e r i z e d in t h e p r e s e n c e of a c i d a n d b a s i c c a t a l y s t s w i t h a v i e w t o i n v e s t i g a t i n g t h e r e a c t i o n c o n d i t i o n s a n d t h e p r o p e r t i e s of t h e r e s u l t i n g p o l y m e r * Vysokomol. soyed. AlO: No. 5, 1122-1126, 1968.
A.M. LOB~NOVet al. REFERENCES
1. L. KLEINER, Plastv~rlden 5: 205, 1955 2. I. M. AL'SHITS, Poliefirnye stekloplastiki dlya sudostroyeniya (Polyester GRPs for Ship-building). Izd. "Sudostroyenie", 1964 3. A. M. KHAIKIN and Kh. A. PARKSHEYAN, Plast. massy, No. 10, 40, 1965 4. V. V. KORSHAK, T. A. SIDOROV, S. V. VINOGRADOVA, L. I. KOMAROVA, P. M. VALETSKII and A. S. LEBEDEVA, Izv. AN SSSR, Chem. series, 261, 1965 5. V. V. KORSHAK, S. V. VINOGRADOVA and A. S. LEBEDEVA, U.S.S.R. Pat. No. 134857, 1960; Byull. izob., No. 1, 1961 6. A. CONIX, Ind. Chim. Belge 22: 1457, 1957 7. V. V. KORSHAK and S. V. VINOGRADOVA, Poliarylaty (Polyarylates). Izd. "Nauka", 1964 8. F. R. MAYO and M. LEWIS, J. Amer. Chem. Soc. 66: 1694, 1944 9. T. ALFREY, D. BORRER and G. MARK, Copolymerization, Foreign Lit. Pub. House, 1953 10. A. V. TOKAREV, Thesis, 1959
THE
EFFECT
OF
RELAXATION
PLASTICIZATION
ON
THE
DIELECTRIC
OF P O L Y M E T H Y L M E T H A C R Y L A T E *
A. M. LOBANOV, D. M. MIRKAMILOV and M. P. PLATO~OV High Molecular Weight Compounds Institute, U.S.S.R. Academy of Sciences (Received 3 J u n e 1967)
IN A n u m b e r of papers [1-4] it was shown t h a t the m o s t probable r e l a x a t i o n time a n d the a c t i v a t i o n e n e r g y of the dipole-group (dipole-radical) process o f polar polymers (polyvinylchloride, p o l y m e t h y l a c r y l a t e , p o l y v i n y l b u t y r a l , polyv i n y l a c e t a t e ) are altered b y the i n t r o d u c t i o n of plasticizers. The most p r o b a b l e r e l a x a t i o n time of the p o l y m e r m a y be d e t e r m i n e d b o t h t h r o u g h t h e intramolecular and also t h r o u g h the interchain interaction. The effect of plasticization on the most probable r e l a x a t i o n time of the dipole-group process indicates t h a t this process depends on the m a g n i t u d e of the interchain interaction which is weakened b y introducing a plasticizer. I t was shown in [5] t h a t when d i b u t y l p h t h a l a t e (DBP) is t h e plasticizer i n t r o d u c e d into p o l y m e t h y l m e t h a c r y l a t e (PMMA) the most p r o b a b l e r e l a x a t i o n time of the dipole-segmental (dipole-elastic) process is reduced, while the m o s t probable relaxation time of the dipole-group process remains constant. Moreover the dielectric losses for the dipole-group process also r e m a i n c o n s t a n t in the region of the m a x i m u m . * Vysokomol. soyed. A10: No. 5, 1116-1121, 1968.
Effect of plasticization on dielectric relaxation of polymethylmethacrylate
1295
On t h e o t h e r h a n d t h e r e is no dielectric dispersion for P M M A soIutions [6-8] in t h e t e m p e r a t u r e a n d f r e q u e n c y region where t h e dipole-group process d e v e l o p s for b u l k PMMA. I n a s t u d y of P M M A plasticized w i t h toluene [7] a t frequencies of 400 c/s a n d a b o v e (i.e. a t frequencies for which t h e r e will be only one region of t a n 5 ~ on a c c o u n t of t h e dipole-group a n d d i p o l e - s e g m e n t a l processes being c o m b i n e d ) it was also s h o w n t h a t as t h e c o n c e n t r a t i o n of t h e plasticizer (toluene) in P M M A increases t h e c o m b i n e d v a l u e o f t a n 5max is displaced into t h e lower t e m p e r a t u r e region, i.e. t h e r e l a x a t i o n t i m e for the c o m b i n e d process is reduced. I n view of t h e a b o v e e x p e r i m e n t a l results it is h a r d to r e a c h a n y definite conclusion r e g a r d i n g t h e effect of p l a s t i c i z a t i o n on t h e dipole-group processes in PMMA. This p a p e r is a s t u d y o f t h e effect of plasticizers on b o t h r e l a x a t i o n processes in PMMA. T h e m e a s u r e m e n t s were car led out a t low frequencies w h e r e t h e " r e s o l u t i o n " of b o t h regions of t h e r e l a x a t i o n process is good.
EXPERIMENTAL The PMMA used for the experiments was obtained by radical polymerization (11//w ~70,000). By repreeipitation in hexane from a solution of the polymer in benzene low molecular weight impurities were removed from the samples, which were dried at 90 ° under a pressure of 10 -2 mmI-Ig. The samples used for the measurements were prepared in film form, the solvent being slowly evaporated from a 20% PMMA solution in toluene. The bottom of the light nickel cup containing the solution to be evaporated served as the lower electrode. The upper electrode was made from aluminium foil while the sample was being prepared. The amount of toluene in the sample was checked after the measurements while the sample was being dried to constant weight. DBP was introduced to PMMA by mechanical mixing in an agate mortar. Samples were press-moulded from a freshly prepared mixture at 150 ° in the form of discs 25-30 mm in dia. and approximately 100-130/l thick. A low-frequency bridge was used for the measurements at frequencies of 1, 5.5, 20 and 70 c/s over the range --60 to 140 °. (The bridge was developed by A. I. Artyuskhov and D. A. Dmitrochenko at the High Molecular Weight Compounds Institute of the U.S.S.R. Academy of Sciences, and was described in [9, 10]. DISCUSSION OF RESULTS
F i g u r e 1 shows t h e results o b t a i n e d b y m e a s u r i n g t a n 5 for P M M A a n d for P M M A plasticized w i t h toluene. I t will be seen t h a t all t h e s a m p l e s o v e r t h e t e m p e r a t u r e i n v e s t i g a t e d h a v e a well defined region o f t a n ~=~x for d i p o l e - s e g m e n t a l a n d d i p o l e - g r o u p processes. T h e region o f t a n ~ a x for b o t h processes is displaced into t h e lower t e m p e r a t u r e region as t h e toluene c o n t e n t of t h e p o l y m e r increases. W h e n the c o n t e n t of toluene in t h e P M M A is increased to 1 3 % t a n 5rex for t h e dipole-group process rises, b u t is r e d u c e d b y f u r t h e r increase ( 2 0 - 3 0 0 ) in t h e toluene content. T h e v a l u e of t a n 5m~x for the d i p o l e - s e g m e n t a l process increases w i t h increase in t h e toluene c o n t e n t o f the PMMA. F i g u r e l a also shows t h a t t h e a d d i t i o n o f toluene to t h e P M M A results in a rel a t i v e l y large d i s p l a c e m e n t of t h e r e g i o n of t a n 5~a~ for t h e d i p o l e - s e g m e n t a l
1296
A , M. LOBANOVet al.
tanO,10 2
J
-50
-~0
-ZO
0
20
~0
GO
80
I
fO0
l
/20
7:. o C
tan, I, lO~
5
,~
I
-#0
-ItO
I
-20
I
0
20
r
40
I
60
,,J
80
I
I
~00
120
140
FIG. I. Tan 6 plotte~[against temperatuxe for samples of P M M _ ~ plasticized~ t h ~oluene at frequencies of 1 (a) and 5.5 c/s (b): 1--0, 2--6.5, 3--13, 4--20 ~ d ~--31% (by wt.) toluene.
Effect of plasticization on dielectric relaxation of polymethylmethaerylate
1297
process compared with the dipole-group process. For example, the addition of 6.5% of toluene displaces the region of tan ~max for the dipole-segmental process b y 36 ° in the lower temperatures direction, b u t b y only 3 ° in the same direction with respect to the dipole-group process. The two processes are therefore combined in the case of certain toluene concentrations. The combination of both processes and the appearance of a single asymmetrical maximum for tan g as the toluene content of the PMMA increases is clearly revealed at a frequency of 5.5 c/s. Figure lb shows that increase in the amount of toluene in the PMMA displaces the combined process into the lower temperature region, and this agrees with the results obtuined in [7]. With a rise in the frequency of the electric field the tan 5 maximum appears at higher temperatures, and the curve becomes les~ asymmetrical. Similar results were obtained for the plasticization of PMMA with the polar plasticizer DBP. Figure 2 shows the curves of tan 5 vs. temperature for plasticized and unplasticized PMMA. It is apparent that with increase in the percentage content of D B P in PM~IA the position of the region of the maximum for the dipolesegmental and dipole-group processes is displaced into the lower temperature region At the same time the value of tan gmax for both dipole-segmental and dipole-group processes increases with a rise in the percentage content of D B P in PMMA. At higher temperatures there is a rise in tan g due to increased electrical conductivity, on account of which the region of tan 5~ax for the dipole-segmental process is smoothed out, and in the case of curve 4 in Fig. 2 does not appear. Figure 3 shows the temperature position of the region of tan 5max for the dipolesegmental (Tmax d.~.) and dipole group (Tmax d.~.) processes plotted against percentage content of toluene and DBP. Figure 3a shows that Tmax d.s. decreases linearly with increase in the percentage content of plasticizer in PMMA. In view of the linear relation of Tmax d.s. tO concentration and also the fact that PMMA is soluble in toluene and D B P it may be concluded that molecular (intrabundle) plasticization [11] takes place in the systems investigated. There is a nonlinear change in Tmax d.g. (Fig. 3b) as the percentage content of plasticizer in the polymer increases. The most marked change in Tmax d.g. occurs with plasticizer concentrations exceeding 10~o. With quite small amounts of plasticizer in PMMA (up to 5-7%) there is only slight change in Tm~x d.g.- Because of this the independence of the temperature position of the region of tan 5max for the dipole-group (dipole-radical) process in relation to the amount of D B P added, which was noted in [5], is due to the small amount of D B P introduced. The rise in tan g~= for both processes with plasticization m a y be due to dipolegroup and dipole-segmental processes being superimposed on one another. The reduction in tan fi~- for the dipole-group process when the PMMA contaifis a certain amount of toluene (Fig. la) is probably due to decrease in the number of polar groups per unit volume of polymer. Displacement of the region of tan g~x for the dipole-segmental process into
1298
A . M . LoBA~ov et al.
the lower temperature region indicates reduction in relaxation time. This is apparently due to the fact that plasticizer molecules reacting with polymer molecules destroy the interchain bonds that had previously existed, and reduce the interchain interaction. The weakening of interchain interaction increases the mobility of the chain segments, and this is reflected in the shorter relaxation time. The absence of change in the most probable relaxation time for the dipolegroup process if small amounts of plasticizer (up to 7%) are added shows t h a t localization plays a greater.part in the dipole-group than in the dipole segmental process. The authors of [5] point out that in PMMA the dipole-group process II ° is due to reorientation of the O = C - - O - - C H a polar group with a small segment of the main carbon chain. With further increase in the plasticizer content the region of tan 5ma* for the dipole-group process is shifted in the direction of lower temperatures, i.e. just as in the case of the dipole-segmental process the relaxation time is reduced. This m a y be connected with increased mobility of the kinetic groups responsible for dipole-group losses, as a result of the reduced interchain
;~an/~28,f0
,l
2 J S !
-40
-ZL7
L7
ZO
40
C0
80
fog
/ZO ~°C
FIG. 2. Tan • plotted against temperature for PMMA samples plasticized with DBP, a t a frequency of 1 e]s: 1--0, 2--7.5, 3--15 and 4--20~o (by wt.) DBP.
Effect of plasticization on dielectric relaxation of polymethylmethacrylate
1299
Tmaxd, ,°C
-wi
b
10
, 20
5
(
,
30' 0 10 Plasticizer, %
,
20
30
FIG. 3. Temperature position of the region of the maximum for dipole-segmental (Tmax d.s.) (a) and dipole-group (Tmaxa.g.) (b) processes plotted against percentage content of toluene (1), DBP (2) ha polymer. Frequency 1 c/s. interaction. This assumption is supported by experimental results regarding the effect of pressure on this process in PMMA [12], and the effect of plasticization on the process of mechanical relaxation [ 13] which occurs with PMMA in the glasslike state, and which is the analogue of the dipole-group process. Thus both the dipole-segmental process and also the dipole-group process depend on the magnitude of interchain interaction. In conclusion we would point out t h a t irrespective of whether the polar group is rigidly attached to the main chain (polyvinylchloride, polyvinylbutyral), or whether internal rotation of the polar group is possible (polymethacrylate, polymethylmethacrylate, polyvinylacetate), the introduction of plasticizer affects the most probable relaxation time of the dipole-group process. CONCLUSIONS
(1) I t has been established t h a t in the plasticization of polymethylmethacrylate by polar and nonpolar plasticizers the relaxation time for the dipole-group and dipole-segmental processes is reduced. (2) The mobility of kinetic groups which are responsible for both the dipolesegmental and also the dipole-group losses depends on the interchain interaction. Translated by R. ft. A. ~IENI)R¥ REFERENCES
1. G. P. MIKkIAII,0V, A. M. LOBANOV and D. M. MIRKAMILOV, Vysokomol. soyed. 8: 1351, 1966 (Translated in Polymer Sei. U.S.S.R. 8: 8, 1483, 1967) 2. G. P. MIK~J.L0V, A. M. LOBANOV and D. M. MIRKAM~L0V, Vysokomol. soyed. A10: 826, 1968 (Translated ha Polymer Sci, U.S.S.R. AID: 4,959, 1968) 3. G. P. M I ~ O V , T. I. BORISOVA and A. 8. NIGMANKHODZHAYEV, Vysokomol. soyed. 9: 991, 1966 (Translated in Polymer Sci. U.S.S.R. 8: 6, 1088, 1966)
1300
Yu. N, SAZANOVet al.
4. P. F. VESELOVSKII and I. A. GANDEL'MAN, Radioelectronika, Trans. Leningrad Polytech. Institute, No. 255, 148, 1965 5. G. P. MIKHAILOV, T. I. BORISOVA and D. A. DMITROCHENKO, Zh. tekhn, fiz. 26: 1924, 1956 6. L. de BROUSKERE, D. BUESS, I. de BOCK and I. VERSLUYS, Bull. Soe. Chim. Belges 64: 669, 1955 7. P. F. VESELOVSKII and V. K. MATVEYEV, Vysokomol. soyed. 6: 1221, 1964 (Translated in Polymer Sci. U.S.S.R. 6: 7, 1345, 1964) 8. G. P. I~[~IAILOV, A. M. LOBANOV and M. P. PLATONOV, Vysokomol. soyed. 8: 692, 1966 (Translated in Polymer Sci. U.S.S.R. 8: 4, 760, 1966) 9. T. NAKAJIMA and D. KONDO, Bull. Electroteehn. Lab. 20: 641, 1956 10. E. SCI~OSSER and G. HORN, Experimentelle Teehnik der Physik. XI: No. 2, 145, 1963 11. P. V. KOZLOV, ZhVKhO ira. Mendeleyeva 9: 660, 1964 12. I. KOPPELMAN and J. GIELESSEN, Kolloid-Z. 175: 97, 1961 13. E. IENKEL and K. ILLERS, Z. Naturforsch., B, A9: No. 5, 440, 1954
POLYMERIZATION OFp,p-bis-CHLOROMETHYL-fl-PROPIOLACTONE Y r . N. SAZA~OV, N. A. GLUK~OV and M. M. KOTO~ High Molecular Weight Compounds Institute, U.S.S.R. Academy of Sciences
(Received 3 July 1967)
I x A previous paper it was shown that the use of fl-lactones as monomers with substituents at the fl-carbon atom is of interest to authors because the synthesis of these monomers presents no difficulties. These lactones are usually produced in a single stage process b y the condensation of ketene with the appropriate earbonyl compounds. I t was shown in [1] following a study of the polymerization of fl,fl-dimethyl-fl-propiolactono that the latter polymerizes very slowly within a very narrow temperature range, and provides relatively low molecular weight compounds; this low activity m a y be the result of the inductive effect of the two methyl groups at the fl-carbon atom reinforcing the alkyl-oxygen bond of the lactone ring, i.e. the bond which opens and causes polymerization of the lactone. In order to weaken the alkyl-oxygen bond electron-acceptor substituents must be i n t r o d u c e d a t t h e f l - c a r b o n a t o m ; e h l o r o m e t h y l g r o u p s w e r e s e l e c t e d as t h e s e s u b s t i t u e n t s , a n d fl,fl-bis-chloromethyl-fl-propiolactone (fl-BCML) w a s s y n t h e s i z e d a n d t h e n p o l y m e r i z e d in t h e p r e s e n c e of a c i d a n d b a s i c c a t a l y s t s w i t h a v i e w t o i n v e s t i g a t i n g t h e r e a c t i o n c o n d i t i o n s a n d t h e p r o p e r t i e s of t h e r e s u l t i n g p o l y m e r * Vysokomol. soyed. AlO: No. 5, 1122-1126, 1968.