CROSSOVER-BEHAVIOR OF DIELECTRIC-RELAXATION IN ISOTACTIC POLYSTYRENE - FROM STRETCHED EXPONENTIAL DECAY TO POWER LAW DECAY

Dielectric loss was studied for the alpha-relaxation of isotactic polystyrene; the relaxation is associated with the micro-Brownian motion of polymer chains in the amorphous phase. The decay function for the relaxation was calculated directly from the dielectric loss. It was found that the dielectric relaxation becomes slower as the degree of crystallinity increases. It was also found that the relaxation undergoes a crossover from a stretched exponential decay to a power law decay as the relaxation proceeds. Crystallized isotactic polystyrene has a definite crossover time, while amorphous isotactic polystyrene undergoes the crossover through an intermediate region.