Dielectric Relaxation in Poly(vinylidene Fluoride): δ Relaxation

The nature of the dielectric δ relaxation observed in poly(vinylidene fluoride) (PVDF) was examined. The δ relaxation was observed only in PVDF consisting of form II crystals. The intensity of the δ relaxation decreased with decreasing crystallinity in form II PVDF and also decreased upon annealing, which increases crystallinity and decreases the amount of crystalline defects. In a copolymer of vinylidene fluoride with form I structure, the δ relaxation was not observed. Thus, it was considered that the δ relaxation was related to molecular motion at disordered sites associated with crystalline defects in form II PVDF. These results are consistent with the mechanism of δ relaxation presented recently.