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The temperature dependence of the monomer reactivity ratios in the copolymerization of styrene with vinyl methyldiacetoxysilane
European Pobmer Journal. Vol 13. pp. 623 to 624. Pergamon Press 1977 Prinled in Great Britain
THE TEMPERATURE DEPENDENCE .OF THE M O N O M E R REACTIVITY RATIOS IN THE COPOLYMERIZATION OF STYRENE WITH VINYL METHYLDIACETOXYSILANE P. BAJAJ, D. C. GUPTA a n d G. N. BABU Indian Institute of Technology. Hauz Khas, New Delhi-110029, India
(Received 10 July 1976: in revisedform 11 November 1976) Abstract--Styrene has been copolymerized with vinylmethyldiacetoxysilane in bulk at tempcratu|es between 60 and 100°, using benzoyl peroxide as initiator. The compositions of copolymers have been determined by the silicon estimation. The reactivity ratios have been calculated by the conventional scheme of copolymerization. Arrhenius parameters have been derived: the energies of activation favour self-propagation whereas the frequency factors favour cross-propagation. INTROD UCTION Styrene has been copolymerized with various vinylsilanes [ I - 5 ] . e.g. vinyltrimethylsilane, vinyldimethylphenylsilane, vinyltriethoxysilane and vinyltrimethoxysilane a n d the reactivity ratios have been determined. T h e effect of temperature on the kinetics of copolymerization of styrene-vinyltriacetoxysiliane (St-VTAS) a n d styrene-I(2 methacryloyloxy)ethoxy]trimethylsilane ( S t - 2 M A E T M S ) has already been reported [6, 7]. In both the systems, r~ (styrene) decreases with increasing polymerization temperature: the influence of temperature on r t is greater for St-VTAS. T h e studies have now been extended to the copolymerization of st$,rene (M j ) with vinylmethyldiacetoxysilane (M_,) to investigate the effect of the substituent in the silane moiety on reactivity ratios.
-o.~
EXPERIMENTAL
-o.1
o
o!t
g-~
Fig. I. Copolymerization of styrene (M ~I with vinyhnethyldiacetoxysilane (M_O at 70 r~ = 8.7 + 0.2. r_, ~ 0.
Styrene and benzoyl peroxide were purified as previously[6]. Vinylmethyldiacetoxysilane (VMDAS) was prepared by treating vinylmethyldichlorosilane with acetic anhydride in 1:2 molar ratio[8]. The fraction between 164-166 ° was collected. Free radical copolymerizations in bulk were carried out in the range 60-100 ~ _+ 0.5 ~ to low conversions in the usual manner [6, 7] with benzoyl peroxide as initiator. The time necessary for low conversions was found from time vs conversion plots. The products were isolated by precipitation in stirred methanol and purified by repeated precipitation. thex were dried at 50 under vacuum to constant weight.
respectively and r 2 ~ 0 (Table I). Similar values were obtained by the Fineman a n d Ross m e t h o d [10]. S t - V M D A S at 60:. r t = 10.3 + 0.3. r 2 -~ 0. at 10@. r I = 5.6 + 0.1. r_~ = 0.
RESULTS AND DISCUSSION Plots were made of r2 against rt for temperatures between 60 a n d 100 ° based on the intersection m e t h o d [9]. Figure 1 shows typical behaviour at 70 °. T h e values obtained for rt at 60 a n d 100: in the S t - V M D A S system were: 10.4 + 0.3 and 5.4 __+0.3.
The mole fractions of styrene in copolymer for various c o m o n o m e r compositions are shown in Fig. 2. In all cases, the copolymers are much richer in styrene than the feed. Moreover. as V M D A S does not homopolymerize under the experimental conditions, one can assume that the copolymer consists of large blocks of styrene units, interrupted by single c o m o n o m e r units. Further. the copolymerization of S t - V M D A S is slower than the h o m o p o l y m e r i z a t i o n of styrene under the identical conditions (Fig. 3). probably because of the lower reactivity of the poly-
Table 1. Variation of reactivity ratios with temperature and Arrhenius parameters for r~ Monomer Styrene (M~)
60 ~
r~ at polymerization temperatures 70 ° 80 ~
10.4 _ 0.3
8.7 + 0.2
7.5 + 0.4 623
E~-E~2 100:
KJ mole- ~
5.4 ___0.3
-8.5 + 0.3
At~ .4~2 0.24 _- 0 1
AS~ AS~2 JK ~ mole - 15.S _+ 0.S
624
P. BAJAJ, D. C. GUPTA and G. N. BABU :'0
2.4
0.9
2"2--
0.8
2-0-
0
I
I 0.2
I
0.4
I
0.~$
0 "8
~.0
1.0--
,% Fig. 2. Copolymerizalion of styrene ( M l ) with vinylmethy]-
diacetoxysilane (M2). Initial copolymer composition vs composition of monomer feed. (1) 60°; (2) 100°.
/'62. 6
2"7
2.8
2.9
3-O
J .I!
,,o ~/;r, ,,,r""!
Fig. 4. Arrhenius plot for r~. 16
!
tl~ 1,z
TZs4E,~ hi"
Fig. 3. Time vs conversion St-VMDAS
plots. (1) Styrene; (2) at 60 °.
meric radical having a silane unit at the reactive end ( " ' M l M~) than the polystyryi radical (,,,Mr M~) The reciprocal of rt can be used as a measure of the relative reactivity of the silane monomers towards polystyryl radical. From the l/r~ values (Table 2), the order of reactivity of the silane monomers towards polystyryl radical is MAETMS > VTAS > VMDAS > VTES. This result may be explained on the basis of resonance and polar factors. The higher reactivity of 2-MAETMS monomer towards polystyryl radical may be related to the resonance stabilization of the vinyl group with carbonyl. On the other hand, although VTAS is bulkier than VMDAS (i.e. substitution o f - - O A C in place of ---CH3 in VMDAS) the reactivity of VTAS is much greater than that of VMDAS suggesting that the effect of the polar nature of the substituent predominates in controlling the copolymerization. A study of the temperature dependence of the reactivity ratios reveals that r~ decreases with increase Table 2. Comparison of the relative reactivities of the silane monomers towards polystyryl radical at 60°
l/r I
VTES
VMDAS
VTAS
2-MAETMS
0.077
0.096
0.260
0.847
VTES, Vinyltriethoxysilane;2-MAETM S, [(2-Methacryloyloxy)ethoxy] trimeth ylsilane.
in copolymerization temperature; this means the tendency of VMDAS monomer to react with polystyryl radical is predominant at higher temperatures. O'Driscoll [11] has pointed out that the only reactivity ratios which will exhibit significant temperature dependence will be those which are very large or very small. The temperature effects observed in this study appear to be consistent with the above statement, as rt is quite high. The Arrhenius plot for St-VMDAS is shown in Fig. 4; Arrhenius parameters are given in Table 1. The difference between activation energies (E~I-E~2) favours self-pr0pagation of the polystyryl radical whilst the ratio of pre-exponential factors All~At2 favours cross-propagation of the polystyryl radical. Acknowledgement--The authors thank the Council of Scientific & Industrial Research, Delhi for providing a Junior Research Fellowship to D. C. Gupta.
REFERENCES
1. N. S. Nametkin, S. G. Durgar'yan and V. G. Filippova, Dokl. Akad. Nauk SSSR 177. 853 (1967); Chem. Abstr. 68, 50108r (1967). 2. V.G. Filippova, N S. Nametkin and S. G. Durgar'yan, l-r. Akad. Nauk SSSR. Ser. Khim. 1727, (1966); Chem. Abstr. 66. 18893r (1967). 3. N. S. Nametkin, S. G. Durgar'yan and V. G. Filippova, Dokl. Akad. Nauk SSSR 172. 1090 (1967); Chem. Abstr. 66, 95413m (1967). 4. Z. M. Rzaev, L. V. Bryksina. Sh. K. Kyazimov and S. I. Sadikh-Zade, Vysokomolek. Soedin. Ser. AI4. 259 (1972}. 5. C. E. Scott and C. C. Price, J. Am. chem. Soc. 81. 2672 {1959). 6. P. Bajaj, Y. P. Khanna and G. N. Babu, J. Polym. Sci. (Chem. Ed.) 14, 465 (1976). 7. P. Bajaj and G. N. Babu, Europ. Polym. J. 12. 601 (1976}. 8. B. N. Dolgov, V. P. Davydova and M. G. Voronkov, Zh. obshch. Khim. 27. 1593 (1957); Chem. Abstr. 52. 3674 ~1958). 9. T. Alfrey Jr., J. J. Bohrer and H. Mark, Copol)'merization. lnterscience, New York. 1952. 10. M. Fineman and J. D. Ross, J. Polym. Sci. ft. 259 (19501. II. K. F. O'DriscoIl, J. Macromol. Sci. A3, 307 (1969).
THE TEMPERATURE DEPENDENCE .OF THE M O N O M E R REACTIVITY RATIOS IN THE COPOLYMERIZATION OF STYRENE WITH VINYL METHYLDIACETOXYSILANE P. BAJAJ, D. C. GUPTA a n d G. N. BABU Indian Institute of Technology. Hauz Khas, New Delhi-110029, India
(Received 10 July 1976: in revisedform 11 November 1976) Abstract--Styrene has been copolymerized with vinylmethyldiacetoxysilane in bulk at tempcratu|es between 60 and 100°, using benzoyl peroxide as initiator. The compositions of copolymers have been determined by the silicon estimation. The reactivity ratios have been calculated by the conventional scheme of copolymerization. Arrhenius parameters have been derived: the energies of activation favour self-propagation whereas the frequency factors favour cross-propagation. INTROD UCTION Styrene has been copolymerized with various vinylsilanes [ I - 5 ] . e.g. vinyltrimethylsilane, vinyldimethylphenylsilane, vinyltriethoxysilane and vinyltrimethoxysilane a n d the reactivity ratios have been determined. T h e effect of temperature on the kinetics of copolymerization of styrene-vinyltriacetoxysiliane (St-VTAS) a n d styrene-I(2 methacryloyloxy)ethoxy]trimethylsilane ( S t - 2 M A E T M S ) has already been reported [6, 7]. In both the systems, r~ (styrene) decreases with increasing polymerization temperature: the influence of temperature on r t is greater for St-VTAS. T h e studies have now been extended to the copolymerization of st$,rene (M j ) with vinylmethyldiacetoxysilane (M_,) to investigate the effect of the substituent in the silane moiety on reactivity ratios.
-o.~
EXPERIMENTAL
-o.1
o
o!t
g-~
Fig. I. Copolymerization of styrene (M ~I with vinyhnethyldiacetoxysilane (M_O at 70 r~ = 8.7 + 0.2. r_, ~ 0.
Styrene and benzoyl peroxide were purified as previously[6]. Vinylmethyldiacetoxysilane (VMDAS) was prepared by treating vinylmethyldichlorosilane with acetic anhydride in 1:2 molar ratio[8]. The fraction between 164-166 ° was collected. Free radical copolymerizations in bulk were carried out in the range 60-100 ~ _+ 0.5 ~ to low conversions in the usual manner [6, 7] with benzoyl peroxide as initiator. The time necessary for low conversions was found from time vs conversion plots. The products were isolated by precipitation in stirred methanol and purified by repeated precipitation. thex were dried at 50 under vacuum to constant weight.
respectively and r 2 ~ 0 (Table I). Similar values were obtained by the Fineman a n d Ross m e t h o d [10]. S t - V M D A S at 60:. r t = 10.3 + 0.3. r 2 -~ 0. at 10@. r I = 5.6 + 0.1. r_~ = 0.
RESULTS AND DISCUSSION Plots were made of r2 against rt for temperatures between 60 a n d 100 ° based on the intersection m e t h o d [9]. Figure 1 shows typical behaviour at 70 °. T h e values obtained for rt at 60 a n d 100: in the S t - V M D A S system were: 10.4 + 0.3 and 5.4 __+0.3.
The mole fractions of styrene in copolymer for various c o m o n o m e r compositions are shown in Fig. 2. In all cases, the copolymers are much richer in styrene than the feed. Moreover. as V M D A S does not homopolymerize under the experimental conditions, one can assume that the copolymer consists of large blocks of styrene units, interrupted by single c o m o n o m e r units. Further. the copolymerization of S t - V M D A S is slower than the h o m o p o l y m e r i z a t i o n of styrene under the identical conditions (Fig. 3). probably because of the lower reactivity of the poly-
Table 1. Variation of reactivity ratios with temperature and Arrhenius parameters for r~ Monomer Styrene (M~)
60 ~
r~ at polymerization temperatures 70 ° 80 ~
10.4 _ 0.3
8.7 + 0.2
7.5 + 0.4 623
E~-E~2 100:
KJ mole- ~
5.4 ___0.3
-8.5 + 0.3
At~ .4~2 0.24 _- 0 1
AS~ AS~2 JK ~ mole - 15.S _+ 0.S
624
P. BAJAJ, D. C. GUPTA and G. N. BABU :'0
2.4
0.9
2"2--
0.8
2-0-
0
I
I 0.2
I
0.4
I
0.~$
0 "8
~.0
1.0--
,% Fig. 2. Copolymerizalion of styrene ( M l ) with vinylmethy]-
diacetoxysilane (M2). Initial copolymer composition vs composition of monomer feed. (1) 60°; (2) 100°.
/'62. 6
2"7
2.8
2.9
3-O
J .I!
,,o ~/;r, ,,,r""!
Fig. 4. Arrhenius plot for r~. 16
!
tl~ 1,z
TZs4E,~ hi"
Fig. 3. Time vs conversion St-VMDAS
plots. (1) Styrene; (2) at 60 °.
meric radical having a silane unit at the reactive end ( " ' M l M~) than the polystyryi radical (,,,Mr M~) The reciprocal of rt can be used as a measure of the relative reactivity of the silane monomers towards polystyryl radical. From the l/r~ values (Table 2), the order of reactivity of the silane monomers towards polystyryl radical is MAETMS > VTAS > VMDAS > VTES. This result may be explained on the basis of resonance and polar factors. The higher reactivity of 2-MAETMS monomer towards polystyryl radical may be related to the resonance stabilization of the vinyl group with carbonyl. On the other hand, although VTAS is bulkier than VMDAS (i.e. substitution o f - - O A C in place of ---CH3 in VMDAS) the reactivity of VTAS is much greater than that of VMDAS suggesting that the effect of the polar nature of the substituent predominates in controlling the copolymerization. A study of the temperature dependence of the reactivity ratios reveals that r~ decreases with increase Table 2. Comparison of the relative reactivities of the silane monomers towards polystyryl radical at 60°
l/r I
VTES
VMDAS
VTAS
2-MAETMS
0.077
0.096
0.260
0.847
VTES, Vinyltriethoxysilane;2-MAETM S, [(2-Methacryloyloxy)ethoxy] trimeth ylsilane.
in copolymerization temperature; this means the tendency of VMDAS monomer to react with polystyryl radical is predominant at higher temperatures. O'Driscoll [11] has pointed out that the only reactivity ratios which will exhibit significant temperature dependence will be those which are very large or very small. The temperature effects observed in this study appear to be consistent with the above statement, as rt is quite high. The Arrhenius plot for St-VMDAS is shown in Fig. 4; Arrhenius parameters are given in Table 1. The difference between activation energies (E~I-E~2) favours self-pr0pagation of the polystyryl radical whilst the ratio of pre-exponential factors All~At2 favours cross-propagation of the polystyryl radical. Acknowledgement--The authors thank the Council of Scientific & Industrial Research, Delhi for providing a Junior Research Fellowship to D. C. Gupta.
REFERENCES
1. N. S. Nametkin, S. G. Durgar'yan and V. G. Filippova, Dokl. Akad. Nauk SSSR 177. 853 (1967); Chem. Abstr. 68, 50108r (1967). 2. V.G. Filippova, N S. Nametkin and S. G. Durgar'yan, l-r. Akad. Nauk SSSR. Ser. Khim. 1727, (1966); Chem. Abstr. 66. 18893r (1967). 3. N. S. Nametkin, S. G. Durgar'yan and V. G. Filippova, Dokl. Akad. Nauk SSSR 172. 1090 (1967); Chem. Abstr. 66, 95413m (1967). 4. Z. M. Rzaev, L. V. Bryksina. Sh. K. Kyazimov and S. I. Sadikh-Zade, Vysokomolek. Soedin. Ser. AI4. 259 (1972}. 5. C. E. Scott and C. C. Price, J. Am. chem. Soc. 81. 2672 {1959). 6. P. Bajaj, Y. P. Khanna and G. N. Babu, J. Polym. Sci. (Chem. Ed.) 14, 465 (1976). 7. P. Bajaj and G. N. Babu, Europ. Polym. J. 12. 601 (1976}. 8. B. N. Dolgov, V. P. Davydova and M. G. Voronkov, Zh. obshch. Khim. 27. 1593 (1957); Chem. Abstr. 52. 3674 ~1958). 9. T. Alfrey Jr., J. J. Bohrer and H. Mark, Copol)'merization. lnterscience, New York. 1952. 10. M. Fineman and J. D. Ross, J. Polym. Sci. ft. 259 (19501. II. K. F. O'DriscoIl, J. Macromol. Sci. A3, 307 (1969).