DIELECTRIC-RELAXATION OF ISOTACTIC POLYSTYRENE AND DEFECT DIFFUSION-MODEL

The alpha-relaxation was investigated by dielectric measurements in both amorphous and isothermally crystallized isotactic polystyrene. The decay function shows a crossover from a stretched-exponential decay (the Williams-Watts equation) to a power-law decay (t(-n)) as the relaxation proceeds. The exponent, n, of the power-law decay increases with decreasing crystallinity and with increasing crystallization temperature. The crossover behavior and its dependence on crystallinity and crystallization temperature could be explained on the basis of a defect diffusion model.