Kinetics of nonisothermal crystallization of sulfonated syndiotactic polystyrene and syndiotactic polystyrene

The kinetics of nonisothermal crystallization has been studied for sulfonated syndiotactic polystyrene (SsPS) containing 1.60mol%,3.05mol% and 4.41mol% sulfo groups, and pure syndiotactic polystyrene (sPS) by means of differential scanning calorimetry (DSC) at various cooling rates. The theory of Mandelkern and the method of Mo Zhishen for nonisothermal crystallization are used to analyze the DSC data. The results show that the crystallization behavior of SsPS exhibits considerable differences in comparison to the neat sample. The degree of crystallinity and the rate of crystallization are significantly lowered by the presence of sulfo groups. The noninteger Avrami exponents,between 2 and 3, for sPS and SsPS samples during nonisothermal crystallization procedure indicate that a mixture of nucleation and growth mechanisms are occurring. On the other hand,the quite comparable Avrami exponents for the sPS and SsPS samples suggests that sulfonation does not significantly alter the observed crystallization mechanism of sPS. In addition, the crystallization activation energies for nonisothermal crystallization are evaluated to be 240.50kJ/mol for sPS, and 251.70kJ/mol, 272.33kJ/mol and 290.79kJ/mol for SsPS containing 1.60mol%, 3.05mol% and 4.41mol% sulfo groups, respectively.