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Miscibility of tetramethyl polycarbonate with syndiotactic polystyrene
PII:
Eur. Polym. J. Vol. 34, No. 8, pp. 1229±1231, 1998 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0014-3057/98 $Ðsee front matter S0014-3057(97)00243-7
SHORT COMMUNICATION MISCIBILITY OF TETRAMETHYL POLYCARBONATE WITH SYNDIOTACTIC POLYSTYRENE KYUNG AH KOH,1 JONG HA KIM,1 DONG HO LEE,2 MUYONG LEE3 and HAN MO JEONG1* 1 Department of Chemistry, University of Ulsan, Ulsan 680-749, Republic of Korea, 2Department of Polymer Science, Kyungpook National University, Taegu 702-701, Republic of Korea and 3Department of Chemical Technology, Seoul National University, Seoul 151-742, Republic of Korea
(Received 10 February 1997; accepted in ®nal form 17 June 1997) AbstractÐTetramethyl polycarbonate (TMPC) and syndiotactic polystyrene (s-PS) are miscible, showing single glass transition temperature in blends. The crystallization behavior of s-PS in blends with TMPC was retarded by the miscible TMPC. The binary interaction energy density B, between TMPC and s-PS was calculated from the melting point depression of s-PS to be ÿ0.92 J/cm3. # 1998 Elsevier Science Ltd. All rights reserved
INTRODUCTION
Tetramethyl polycarbonate (TMPC) is miscible with many kinds of polymers, including styrenic copolymers and aliphatic polyesters [1±3]. Stereoregularity may in¯uence the miscibility of polymer blends [4, 5]. Some papers have reported on the miscibility behaviors of syndiotactic polystyrene (s-PS) with other polymers, such as poly(vinyl methyl ether) and poly(2,6-dimethyl-1,4phenylene oxide) [6, 7]. TMPC is known to be miscible with atactic polystyrene [8]. In this paper, we report the results on the miscibility studies on blends of TMPC and sPS. EXPERIMENTAL
TMPC was synthesized by the reaction of tetramethyl bisphenol-A (Tokyo Kasei) and triphosgene (Aldrich) in 1,2-dichloroethane in the presence of pyridine at room temperature for 5 h. The reaction mixture was poured into 10-fold of methanol. And the ®ltered precipitate was dried under vacuum at 708C after washing with methanol. Number average molecular weight (Mn) and weight average molecular weight (Mw) of TMPC, determined by GPC using polystyrene standards, were 4,300 and 16,800 respectively. s-PS (Dow Chemical, Mn=218,000, Mw=470,000) was puri®ed by dissolution in 1,2-dichlorobenzene containing about 2 wt% conc. HCl at 508C, followed by precipitation in an excess of methanol. The TMPC/s-PS blends were prepared by a dissolution± precipitation method. The polymers were dissolved in 1,2dichlorobenzene at 508C to give a concentration of about 5% (w/v). This solution was added to 10-fold of methanol, causing a rapid precipitation. The precipitate was ®ltered o and dried under vacuum at 708C. A dierential scanning calorimeter (TA Instruments DSC-2100) was used to measure thermal properties. Each *To whom all correspondence should be addressed.
sample was annealed at 2908C for 2 min, and cooled down to 308C with the cooling rate of 208C/min to measure crystallization temperature (Tmc) and heat of crystallization (DHmc). On the subsequent heating from 308C to 2908C at a heating rate of 208C/min, glass transition temperature (Tg) and melting temperature (Tm) were measured. To obtain Homan±Weeks plot for determining equilibrium melting temperature of s-PS [9], sample was melted at 2908C for 2 min, and then rapidly cooled down to crystallization temperature (Tc) where it was held for 20 min prior to reheating at 208C/min to measure melting temperature.
RESULTS AND DISCUSSION
Table 1 shows Tg values of the blends which vary with composition. This indicates that these two polymers are miscible. The Tg-composition data of miscible polymer blends can be represented by the following Gordon±Taylor equation. Tgb
w1 Tg1 kw2 Tg2 w1 kw2
1
where Tgb is the Tg of the miscible blend, Tg1 and Tg2, w1 and w2 are the Tg values and the weight fractions of the component polymers, and k is an adjustable parameter related to the degree of curvature of the Tg-composition curve. The values of k are often related to the strength of the interactions between component polymers: with higher k values for stronger intermolecular interactions. The k value obtained for TMPC/s-PS blend was 0.60, showing that the intermolecular interaction is not so strong to restrict chain mobility [10]. In Table 1, we can see that the Tm of s-PS decreases as the content of TMPC in blend increases and no endothermic melting peak for TMPC-rich compositions are observed. This melting point depression of s-PS is also ascribable to
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Short communication Table 1. Thermal properties of TMPC/s-PS blends Weight ratio of TMPC/s-PS
Tg (K)
Tm (K)
Tmc (K)
0/100 20/80 40/60 60/40 80/20 100/0
372.6 379.1 404.3 418.5 441.7 466.4
543.4 542.1 540.1 ÿ ÿ ÿ
504.7 500.3 478.9 ÿ ÿ ÿ
the miscibility with TMPC. A melting point depression in polymer blends, when one component (component 2) is crystallizable, can be expressed by the equation (2), when both components are of large molecular weight and the contribution by entropy can be neglected [9]. DT
0 m
T
0 m2
ÿT
0 m2b
ÿ
V2u BF21 T DH2u
0 m2
2
In this equation, T0m2 and T0m2b are the equilibrium melting temperature of crystallizable component in pure state and in blend respectively, DH2u/V2u is its heat of fusion per unit volume for 100% crystallinity, F1 is the volume fraction of the other component in the amorphous phase, and B is binary interaction energy density. The equilibrium melting temperature for the quantitative analysis by equation (2) is determined by DSC from Homan± Weeks plot [9, 11]. Figure 1 show the endothermic melting peaks of s-PS isothermally crystallized at
Fig. 1. DSC thermogram of s-PS crystallized isothermally at (a) 241.08C, (b) 250.08C, (c) 253.08C, and (d) 256.58C.
DHmc (J/g-s-PS) 18.3 21.3 14.2 ÿ ÿ ÿ
various crystallization temperature (Tc). This multiple endothermic melting behavior was similarly observed with isotactic polystyrene. And the peak at the lowest temperature was ascribed to the melting of the material crystallized by secondary crystallization, and the peak at the highest temperature was ascribed to the melting of crystallites formed at Tc but reorganized during the heating [12]. So, we chose the second melting peak as the melting of crystals formed at Tc for Homan±Weeks plot. All the observed melting temperatures increase linearly with the crystallization temperature, and the experimental data are extrapolated to Tm=Tc line by the least square analysis to obtain the equilibrium melting temperature. The T0m2 for s-PS and the T0m2b for 20/80 and 40/60 TMPC/s-PS blends were 554.7 K, 549.5 K, and 548.2 K respectively. If we assume that B is independent of composition, we can calculate B using the slope of the line in Fig. 2. By assuming that the densities of TMPC and s-PS are both 1.08 g/cm3 at 308C [13], and DH2u/V2u is 45 J/ cm3 [14, 15], the calculated B value was ÿ0.92 J/ cm3. This value of B is similar with that of TMPC/ a-PS blend(ÿ0.63 J/cm3) reported previously [16]. Small positive intercept on the DTm axis of Fig. 2 seems to be due to the contribution by entropy neglected in equation (2), as observed in many other instances [9, 17]. Table 1 also show increased supercooling necessary for the crystallization of s-PS, TmÿTmc and decreased heat of crystallization, DTmc at high content of TMPC. These results show that the miscible TMPC retards the crystallization of s-PS.
Fig. 2. Plot of DT0m vs F21 for TMPC/s-PS blends.
Short communication REFERENCES
1. Kim, C. K. and Paul, D. R., Polymer, 1992, 33, 2089. 2. Fernandes, A. C., Barlow, J. W. and Paul, D. R., Polymer, 1986, 27, 1799. 3. Hellmann, E. H., Hellmann, G. P. and Rennie, A. R., Colloid Polym. Sci., 1991, 269, 343. 4. Beaucage, G. and Stein, R. S., Macromolecules, 1993, 26, 1603. 5. Ueda, H. and Karasz, F. E., Polym. J., 1994, 26, 771. 6. Cimmino, S., Di Pace, E., Martuscelli, E. and Silvestre, C., Polymer, 1993, 34, 2799. 7. Guerra, G., De Rosa, C., Vitagliano, V. M., Petraccone, V., Corradini, P. and Karasz, F. E., Polym. Commun., 1991, 32, 30. 8. Kim, C. K. and Paul, D. R., Polymer, 1992, 33, 1630.
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9. Nishi, T. and Wang, T. T., Macromolecules, 1975, 8, 909. 10. Pomposo, J. A., Eguiazabal, I., Calahorra, E. and CortaÂzar, M., Polymer, 1993, 34, 95. 11. de Juana, R. and CortaÂzar, M., Macromolecules, 1993, 26, 1170. 12. Amelino, L., Martuscelli, E., Sellitti, C. and Silvestre, C., Polymer, 1990, 31, 1051. 13. Kim, C. K. and Paul, D. R., Polymer, 1992, 33, 1630. 14. Su, Z., Li, X. and Hsu, S. L., Macromolecules, 1994, 27, 287. 15. Greis, O., Xu, Y., Asano, T. and Petermann, J., Polymer, 1989, 30, 590. 16. Kim, C. K. and Paul, D. R., Polymer, 1992, 33, 4941. 17. Ziska, J. J., Barlow, J. W. and Paul, D. R., Polymer, 1981, 22, 918.
Eur. Polym. J. Vol. 34, No. 8, pp. 1229±1231, 1998 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0014-3057/98 $Ðsee front matter S0014-3057(97)00243-7
SHORT COMMUNICATION MISCIBILITY OF TETRAMETHYL POLYCARBONATE WITH SYNDIOTACTIC POLYSTYRENE KYUNG AH KOH,1 JONG HA KIM,1 DONG HO LEE,2 MUYONG LEE3 and HAN MO JEONG1* 1 Department of Chemistry, University of Ulsan, Ulsan 680-749, Republic of Korea, 2Department of Polymer Science, Kyungpook National University, Taegu 702-701, Republic of Korea and 3Department of Chemical Technology, Seoul National University, Seoul 151-742, Republic of Korea
(Received 10 February 1997; accepted in ®nal form 17 June 1997) AbstractÐTetramethyl polycarbonate (TMPC) and syndiotactic polystyrene (s-PS) are miscible, showing single glass transition temperature in blends. The crystallization behavior of s-PS in blends with TMPC was retarded by the miscible TMPC. The binary interaction energy density B, between TMPC and s-PS was calculated from the melting point depression of s-PS to be ÿ0.92 J/cm3. # 1998 Elsevier Science Ltd. All rights reserved
INTRODUCTION
Tetramethyl polycarbonate (TMPC) is miscible with many kinds of polymers, including styrenic copolymers and aliphatic polyesters [1±3]. Stereoregularity may in¯uence the miscibility of polymer blends [4, 5]. Some papers have reported on the miscibility behaviors of syndiotactic polystyrene (s-PS) with other polymers, such as poly(vinyl methyl ether) and poly(2,6-dimethyl-1,4phenylene oxide) [6, 7]. TMPC is known to be miscible with atactic polystyrene [8]. In this paper, we report the results on the miscibility studies on blends of TMPC and sPS. EXPERIMENTAL
TMPC was synthesized by the reaction of tetramethyl bisphenol-A (Tokyo Kasei) and triphosgene (Aldrich) in 1,2-dichloroethane in the presence of pyridine at room temperature for 5 h. The reaction mixture was poured into 10-fold of methanol. And the ®ltered precipitate was dried under vacuum at 708C after washing with methanol. Number average molecular weight (Mn) and weight average molecular weight (Mw) of TMPC, determined by GPC using polystyrene standards, were 4,300 and 16,800 respectively. s-PS (Dow Chemical, Mn=218,000, Mw=470,000) was puri®ed by dissolution in 1,2-dichlorobenzene containing about 2 wt% conc. HCl at 508C, followed by precipitation in an excess of methanol. The TMPC/s-PS blends were prepared by a dissolution± precipitation method. The polymers were dissolved in 1,2dichlorobenzene at 508C to give a concentration of about 5% (w/v). This solution was added to 10-fold of methanol, causing a rapid precipitation. The precipitate was ®ltered o and dried under vacuum at 708C. A dierential scanning calorimeter (TA Instruments DSC-2100) was used to measure thermal properties. Each *To whom all correspondence should be addressed.
sample was annealed at 2908C for 2 min, and cooled down to 308C with the cooling rate of 208C/min to measure crystallization temperature (Tmc) and heat of crystallization (DHmc). On the subsequent heating from 308C to 2908C at a heating rate of 208C/min, glass transition temperature (Tg) and melting temperature (Tm) were measured. To obtain Homan±Weeks plot for determining equilibrium melting temperature of s-PS [9], sample was melted at 2908C for 2 min, and then rapidly cooled down to crystallization temperature (Tc) where it was held for 20 min prior to reheating at 208C/min to measure melting temperature.
RESULTS AND DISCUSSION
Table 1 shows Tg values of the blends which vary with composition. This indicates that these two polymers are miscible. The Tg-composition data of miscible polymer blends can be represented by the following Gordon±Taylor equation. Tgb
w1 Tg1 kw2 Tg2 w1 kw2
1
where Tgb is the Tg of the miscible blend, Tg1 and Tg2, w1 and w2 are the Tg values and the weight fractions of the component polymers, and k is an adjustable parameter related to the degree of curvature of the Tg-composition curve. The values of k are often related to the strength of the interactions between component polymers: with higher k values for stronger intermolecular interactions. The k value obtained for TMPC/s-PS blend was 0.60, showing that the intermolecular interaction is not so strong to restrict chain mobility [10]. In Table 1, we can see that the Tm of s-PS decreases as the content of TMPC in blend increases and no endothermic melting peak for TMPC-rich compositions are observed. This melting point depression of s-PS is also ascribable to
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Short communication Table 1. Thermal properties of TMPC/s-PS blends Weight ratio of TMPC/s-PS
Tg (K)
Tm (K)
Tmc (K)
0/100 20/80 40/60 60/40 80/20 100/0
372.6 379.1 404.3 418.5 441.7 466.4
543.4 542.1 540.1 ÿ ÿ ÿ
504.7 500.3 478.9 ÿ ÿ ÿ
the miscibility with TMPC. A melting point depression in polymer blends, when one component (component 2) is crystallizable, can be expressed by the equation (2), when both components are of large molecular weight and the contribution by entropy can be neglected [9]. DT
0 m
T
0 m2
ÿT
0 m2b
ÿ
V2u BF21 T DH2u
0 m2
2
In this equation, T0m2 and T0m2b are the equilibrium melting temperature of crystallizable component in pure state and in blend respectively, DH2u/V2u is its heat of fusion per unit volume for 100% crystallinity, F1 is the volume fraction of the other component in the amorphous phase, and B is binary interaction energy density. The equilibrium melting temperature for the quantitative analysis by equation (2) is determined by DSC from Homan± Weeks plot [9, 11]. Figure 1 show the endothermic melting peaks of s-PS isothermally crystallized at
Fig. 1. DSC thermogram of s-PS crystallized isothermally at (a) 241.08C, (b) 250.08C, (c) 253.08C, and (d) 256.58C.
DHmc (J/g-s-PS) 18.3 21.3 14.2 ÿ ÿ ÿ
various crystallization temperature (Tc). This multiple endothermic melting behavior was similarly observed with isotactic polystyrene. And the peak at the lowest temperature was ascribed to the melting of the material crystallized by secondary crystallization, and the peak at the highest temperature was ascribed to the melting of crystallites formed at Tc but reorganized during the heating [12]. So, we chose the second melting peak as the melting of crystals formed at Tc for Homan±Weeks plot. All the observed melting temperatures increase linearly with the crystallization temperature, and the experimental data are extrapolated to Tm=Tc line by the least square analysis to obtain the equilibrium melting temperature. The T0m2 for s-PS and the T0m2b for 20/80 and 40/60 TMPC/s-PS blends were 554.7 K, 549.5 K, and 548.2 K respectively. If we assume that B is independent of composition, we can calculate B using the slope of the line in Fig. 2. By assuming that the densities of TMPC and s-PS are both 1.08 g/cm3 at 308C [13], and DH2u/V2u is 45 J/ cm3 [14, 15], the calculated B value was ÿ0.92 J/ cm3. This value of B is similar with that of TMPC/ a-PS blend(ÿ0.63 J/cm3) reported previously [16]. Small positive intercept on the DTm axis of Fig. 2 seems to be due to the contribution by entropy neglected in equation (2), as observed in many other instances [9, 17]. Table 1 also show increased supercooling necessary for the crystallization of s-PS, TmÿTmc and decreased heat of crystallization, DTmc at high content of TMPC. These results show that the miscible TMPC retards the crystallization of s-PS.
Fig. 2. Plot of DT0m vs F21 for TMPC/s-PS blends.
Short communication REFERENCES
1. Kim, C. K. and Paul, D. R., Polymer, 1992, 33, 2089. 2. Fernandes, A. C., Barlow, J. W. and Paul, D. R., Polymer, 1986, 27, 1799. 3. Hellmann, E. H., Hellmann, G. P. and Rennie, A. R., Colloid Polym. Sci., 1991, 269, 343. 4. Beaucage, G. and Stein, R. S., Macromolecules, 1993, 26, 1603. 5. Ueda, H. and Karasz, F. E., Polym. J., 1994, 26, 771. 6. Cimmino, S., Di Pace, E., Martuscelli, E. and Silvestre, C., Polymer, 1993, 34, 2799. 7. Guerra, G., De Rosa, C., Vitagliano, V. M., Petraccone, V., Corradini, P. and Karasz, F. E., Polym. Commun., 1991, 32, 30. 8. Kim, C. K. and Paul, D. R., Polymer, 1992, 33, 1630.
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9. Nishi, T. and Wang, T. T., Macromolecules, 1975, 8, 909. 10. Pomposo, J. A., Eguiazabal, I., Calahorra, E. and CortaÂzar, M., Polymer, 1993, 34, 95. 11. de Juana, R. and CortaÂzar, M., Macromolecules, 1993, 26, 1170. 12. Amelino, L., Martuscelli, E., Sellitti, C. and Silvestre, C., Polymer, 1990, 31, 1051. 13. Kim, C. K. and Paul, D. R., Polymer, 1992, 33, 1630. 14. Su, Z., Li, X. and Hsu, S. L., Macromolecules, 1994, 27, 287. 15. Greis, O., Xu, Y., Asano, T. and Petermann, J., Polymer, 1989, 30, 590. 16. Kim, C. K. and Paul, D. R., Polymer, 1992, 33, 4941. 17. Ziska, J. J., Barlow, J. W. and Paul, D. R., Polymer, 1981, 22, 918.