Peculiarities of dielectric relaxation in poly(vinylidene fluoride) with different thermal history

A method of broad-band dielectric relaxation spectroscopy (10−1-107 Hz) has been used to study the relaxation processes in the region of melting in two isotropic poly(vinylidene fluoride) films prepared by way of crystallization from melts under different conditions. The intensive relaxation process observed is attributed to manifestation of a space charge formed by extrinsic carriers. The relaxation time and the intensity of the process reduce when the crystallinity increases. This is related to the increase of extrinsic carriers' mobility in the amorphous areas. It is supposed that at isothermal crystallization there are more chemical defects (end groups, branches, HHTT-type defects) in amorphous areas. Such defects may impede compact chain packing in the amorphous domains and provide conditions for a higher level of mobility of free carriers.