Preparation of PVDF flexible piezoelectric film with high β-phase content by matching solvent dipole moment and crystallization temperature

Abstract

In Poly(vinylidene fluoride) (PVDF) polymer films, α-phase usually dominates and leads to weak electrical properties, limiting its applications in microelectronics. In this paper, the effects of dipole moment of the solvent and the crystallization temperature on β-phase content in PVDF films have been systematically investigated. Variations in crystalline phases were confirmed by using X-ray diffractometer (XRD), Fourier transform infrared spectra (FTIR) and differential scanning calorimetry (DSC). The results verified that larger dipole moment of the solvent is more beneficial to the formation of β-phase in PVDF films. PVDF films with high content of β-phase up to 98.8% are obtained by using dimethylsulfoxide (DMSO) as the solvent at optimized crystallizing temperature of 60 °C. The corresponding PVDF film with high β-phase content presents excellent ferroelectric and piezoelectric properties, with a remnant polarization (Pr) and piezoelectric coefficient (d33) of 7.7 μC/cm2 and − 25.8 pC/N, respectively. It is worth mentioning that this high d33 compares that of the expensive PVDF-based copolymers and complexes. The process displayed in this research provided a feasible method to the preparation of low cost PVDF films for flexible piezoelectric sensors and actuators.