Significantly Enhanced Piezoelectricity of Poly(Vinylidene Fluoride) via Orienting Nanobound State Ions

Abstract

Poly(vinylidene fluoride) (PVDF) demonstrates great potential for applications in flexible sensing and energy harvesting but the piezoelectric coefficient is less than 30 pm V⁻¹ even with the full beta phase. Herein, an all-organic composite of PVDF with ionic liquid (IL) is manufactured through stretching, constrained annealing, and polarization. The DFT and XPS indicate strong ionic dipole interactions between PVDF and IL, favoring the orientation and crystallization of PVDF. Surprisingly, the nanobound states ions achieve orientation in different physical fields, providing ionic dipole enhances the piezoelectricity of the composite films, confirmed by variable temperature dielectric properties, FTIR and XRD. An inverse piezoelectric coefficient of 51.8 pm V⁻¹, obtained from PVDF containing 0.75 wt.% IL, improved by 116% compared to commercial PVDF (≈24 pm V⁻¹). This work presents a novel composite strategy for the fabrication of high piezoelectric flexible polymers.