Dielectric materials can store and release electrical energy quickly and efficiently and have potential applications in the fields of rail transportation, air and space detection, and electromagnetic weapons. However, the most promising dielectric polymer composites under research suffer either from unsatisfactory energy density (U e ) or from increasing the U e at the cost of energy efficiency (η). Herein, by the solution casting method, a nanocomposite film is fabricated by introducing trace selfassembly phase-transitioned lysozyme (PTL) modified boron nitride nanosheets (mBNNS) into a blend matrix consisting of poly(vinylidene fluoride−hexafluoropropylene) P(VDF−HFP) and poly(methyl methacrylate) (PMMA). The results suggest that PTL helps improve the interfacial compatibility of the corresponding nanocomposites via hydrogen-bonding interaction effectively. The nanocomposite film with 5 wt % mBNNS shows remarkably enhanced breakdown strength (E b ) of ∼500 MV/m and U e of 14.9 J/cm 3 , which are 166% and 244% of the blend matrix, respectively. Meanwhile, η of the nanocomposite film reaches ∼71% because of the clipping effect of linear PMMA on the large ferroelectric crystal phase of P(VDF−HFP) and the barrier effect of the highly insulating two-dimensional (2D) mBNNS, which effectively reduces the relaxation and leakage losses. Our research results show that by using a low-loss matrix and trace high-insulation 2D nanosheets, it is possible to achieve dielectric materials with high η and high U e at the same time.

Poly(vinylidene fluoride) (PVDF)-based relaxor ferroelectric polymers, synthesized from the physical or chemical modification of β-PVDF and P(VDF−TrFE) (TrFE refers trifluoroethylene), show high thickness strain under an external field, which allows them to be employed as electroactive materials for actuation, sensor, and artificial muscle applications. In an effort to disclose the formation mechanism of electrostrain, a series of P(VDF−TrFE−CTFE) (CTFE is chlorotrifluoroethylene) copolymers are synthesized and carefully characterized. By correlating the crystalline and ferroelectric phase transitions to their dielectric, ferroelectric, and electromechanical performances, a new model combining both the Maxwell stress and electrostrictive effect is proposed. The contribution of each effect to the overall strain and its dependence on the electric field, material composition, and the fabrication process of the films have been well addressed. The perfect synergism of two effects is responsible for the large strain under a low field, which offers a strategy to design and fabricate electroactive polymers with excellent electrostrain performances.

Poly(vinylidene fluoride) (PVDF) based relaxor ferroelectric polymers show great potential application in transducers, sensors and artificial muscles for their excellent electrostrictive properties. The all-trans chain conformation of current relaxor has...