Composition Dependence of Microstructures and Ferroelectric Properties in Poly(vinylidene fluoride-<i>ter</i>-trifluoroethylene-<i>ter</i>-chlorodifluoroethylene) Terpolymers
Wenhan Xu, Zhubing Han, Yang Liu, Xin Chen, He Li, Lulu Ren, Qiming Zhang, Qing Wang
Abstract
A family of poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorodifluoroethylene) [P(VDF-TrFE-CDFE)] terpolymers was synthesized. The effect of the chlorodifluoroethylene (CDFE) concentration on the microstructures and ferroelectric properties of the terpolymer has been systematically investigated. It is found that P(VDF-TrFE-CDFE) can be gradually converted from a normal ferroelectric into a ferroelectric relaxor with the increase of the CDFE content from 0.7 to 4.5 mol %. Fourier-transform infrared spectroscopy and wide-angle X-ray diffraction reveal that CDFE is incorporated into the crystalline region and breaks up large ferroelectric domains into nanoregions by stabilizing the gauche conformation. As a result, CDFE eliminates the energy barrier of the ferroelectric–paraelectric transition and leads to the relaxor behavior of the terpolymers at high contents of CDFE, including diffuse dielectric peaks, high dielectric constants (e.g. K = 30@room temperature), and slim polarization hysteresis loops. This work identifies a new structure of the ferroelectric relaxor and provides insights into the role of chlorinated comonomers in the polyvinylidene fluoride-based ferroelectric polymers.