Tuning phase transition and ferroelectric properties of poly(vinylidene fluoride-co-trifluoroethylene) via grafting with desired poly(methacrylic ester)s as side chains

Abstract

For potential application in high energy storage capacitors with high energy density and low energy loss, three sets of poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] grafted with poly(methacrylic ester)s, including poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(butyl methacrylate) (PBMA) copolymers, are designed and investigated carefully. Due to their intermediate polarity, relatively high glass transition temperature, and excellent compatibility with PVDF chains, the poly(methacrylic ester) segments introduced could not only dramatically weaken the coupling interactions of oriented polar crystals, but could also accelerate the reversal switching of polar crystal domains along the applied electric field, which leads to well hindered remnant polarization. As a result, the displacement–electric field (D–E) hysteresis behaviors of the graft copolymers could be tuned from typical ferroelectric to either antiferroelectric or linear shape under high electric field. Meanwhile, significantly reduced energy loss and effectively improved energy discharging efficiency were obtained. Compared with PMMA and PBMA, PEMA with intermediate polarity and grafting length exhibits more suitable confinement of the F–P transition of P(VDF-TrFE-CTFE), and thus more desirable energy storage properties are observed in the resultant copolymers. These findings may help to deeply understand the ferroelectric nature of PVDF based fluoropolymers and design new energy storage capacitor materials with high discharged energy density and low energy loss.