Electrical storage in poly(vinylidene fluoride) based ferroelectric polymers: Correlating polymer structure to electrical breakdown strength

A series of poly(vinylidene fluoride) (PVDF) based ferroelectric polymes were synthesized to examine the correlation between the chemical structure and the dielectric breakdown strength. The synthesis of the ferroelectric terpolymer of vinylidene fluoride, chlorotrifluoroethylene (CTFE), and trifluoroethylene (TrFE), P(VDF-CTFE-TrFE), involved copolymerization of VDF andCTFE followed by reductive d4chlorination of CTFE. Wide-angle X-ray diffraction measurements were performed to investigate the evolution of thecrystallinity of the polymers with chemical compositions. The observed positive dependence of breakdown strength on crystallinity and modulus suggested that the electromechanical breakdown mechanism is primarily responsible for electrical failure in these polymers. It has also been also observed that the electromechanical stress is dominated by the Maxwell sress for the ferroelectric polymers with low crystalinity.