Confinement-Induced High-Field Antiferroelectric-like Behavior in a Poly(vinylidene fluoride-co-trifluoroethylene-cochlorotrifluoroethylene)-graft-polystyrene Graft Copolymer

摘要

An antiferroelectric-like polymer approach was proposed for high electric energy storage and low loss performance by using a novel confinement concept. A poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene)-graftpolystyrene [P(VDF-TrFE-CTFE)-g-PS] graft copolymer with 14 wt % PS side chains was successfully synthesized. On the basis of the electric displacement-electric field loop study, a novel antiferroelectric-like behavior with extremely low remanent polarization was achieved in this graft copolymer even when the poling field reached as high as 400 MV/m. Compared with a P(VDF-TrFE) random copolymer having the same TrFE content, a similar discharged energy density but a much lower hysteresis loss was observed. This novel antiferroelectric-like behavior at high poling fields was explained by the confinement (or insulation) effect. After crystallization-induced microphase separation, PS side chains were segregated to the periphery of P(VDF-TrFE) crystals, forming a nanoscale interfacial confining (or insulation) layer. Because of the low polarizability of this confining layer, the compensation polarization at the amorphous-crystalline interface was reduced, and thus the local polarization field became weaker than the local depolarization field. Upon discharging, therefore, a fast dipole reversal and an antiferroelectric-like behavior were achieved even at high poling fields. This study will help us design new polar dielectric polymers for high electric energy storage and low loss applications.