Microstructures and Dielectric Properties of the Ferroelectric Fluoropolymers Synthesized via Reductive Dechlorination of Poly(vinylidene fluoride-co-chlorotrifluoroethylene)s

Ferroelectric fluoropolymers containing vinylidene fluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE) have been prepared over a wide composition range by a two-step approach consisting of copolymerization of VDF and CTFE and a subsequent reductive dechlorination reaction. Due to the similar reactive ratios between VDF and CTFE and quantitative dechlorination yields, the chemical structures and compositions of the resulting terpolymers can be precisely controlled. The structural characteristics including microstructure, chain conformation, and crystallinity of the polymers have been carefully elucidated as a function of the chemical composition by 1H and 19F NMR, Fourier transform infrared spectroscopy, and wide-angle X-ray diffraction. The influence of the polymer compositions on thermal transitions and dielectric constants has also been investigated. A Curie temperature of 23 °C and dielectric constant of 50 measured at ambient temperature and 1 kHz have been achieved at the terpolymer composition of 78.8 mol % VDF, 14 mol % CTFE, and 7.2 mol % TrFE.