A unique relaxor ferroelectric P(VDF-TrFE-CTFE) is investigated as a matrix of SPEs. The P(VDF-TrFE-CTFE) with ultrahigh ε_r promotes the dissociation of LiTFSI to greatly enhance the ionic conductivity and the transference number of lithium ions.

Piezoelectric polymers hold great potential for various electromechanical applications, but only show low performance, with |d₃₃ | < 30 pC/N. We prepare a highly piezoelectric polymer (d₃₃ = −62 pC/N) based on a biaxially oriented poly(vinylidene fluoride) (BOPVDF, crystallinity = 0.52). After unidirectional poling, macroscopically aligned samples with pure β crystals are achieved, which show a high spontaneous polarization (P_s) of 140 mC/m². Given the theoretical limit of P_s,β = 188 mC/m² for the neat β crystal, the high P_s cannot be explained by the crystalline-amorphous two-phase model (i.e., P_s,β = 270 mC/m²). Instead, we deduce that a significant amount (at least 0.25) of an oriented amorphous fraction (OAF) must be present between these two phases. Experimental data suggest that the mobile OAF resulted in the negative and high d₃₃ for the poled BOPVDF. The plausibility of this conclusion is supported by molecular dynamics simulations.

Poly(vinylidene fluoride) (PVDF)‐based polymers demonstrate great potential for applications in flexible and wearable electronics but show low piezoelectric coefficients (e.g., −d₃₃ < 30 pC N⁻¹). The effective improvement for the piezoelectricity of PVDF is achieved by manipulating its semicrystalline structures. However, there is still a debate about which component is the primary contributor to piezoelectricity. Therefore, current methods to improve the piezoelectricity of PVDF can be classified into modulations of the amorphous phase, the crystalline region, and the crystalline–amorphous interface. Here, the basic principles and measurements of piezoelectric coefficients for soft polymers are first discussed. Then, three different categories of structural modulations are reviewed. In each category, the physical understanding and strategies to improve the piezoelectric performance of PVDF are discussed. In particular, the crucial role of the oriented amorphous fraction at the crystalline–amorphous interface in determining the piezoelectricity of PVDF is emphasized. At last, the future development of high performance piezoelectric polymers is outlooked.

Poly(vinylidene fluoride) (PVDF) and its random copolymers exhibit the most distinctive ferroelectric properties; however, their spontaneous polarization (60–105 mC m⁻²) is still inferior to those (>200 mC m⁻²) of the ceramic counterparts. In this work, we report an unprecedented spontaneous polarization (P_s = 140 mC m⁻²) for a highly poled biaxially oriented PVDF (BOPVDF) film, which contains a pure β crystalline phase. Given the crystallinity of ∼0.52, the P_s for the β phase (P_s,β) is calculated to be 279 mC m⁻², if a simple two-phase model of semicrystalline polymers is assumed. This high P_s,β is invalid, because the theoretical limit of P_s,β is 185 mC m⁻², as calculated by density functional theory. To explain such a high P_s for the poled BOPVDF, a third component in the amorphous phase must participate in the ferroelectric switching to contribute to the P_s. Namely, an oriented amorphous fraction (OAF) links the lamellar crystal and the mobile amorphous fraction. From the hysteresis loop study, the OAF content was determined to be ∼0.28, more than 50% of the amorphous phase. Because of the high polarizability of the OAFs, the dielectric constant of the poled BOPVDF reached nearly twice the value of conventional PVDF. The fundamental knowledge obtained from this study will provide a solid foundation for the future development of PVDF-based high performance electroactive polymers for wearable electronics and soft robotic applications.