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

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)-graft-polystyrene [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.