Optimizing solvent dipole moment enables PVDF to improve piezoelectric performance

The all-trans conformation (β-phase) possesses a significant impact on the piezoelectric polymer polyvinylidene fluoride (PVDF). Inducing more molecular chain [-CH₂-CF₂-]nto form all-trans conformation is one of the biggest obstacles for manufacturing high-performance piezoelectric sensing devices. Herein, the continuous vacuum technology is used to modulate the polarity of binary solvents by the proportion of the lower solvent. The regulated solvent forms a high dipole moment, an interaction between the dipole ofβ-phase and the dipole moment makes the phase reversal in PVDF. Fourier transform infrared spectroscopy, piezoelectric constant test and other characterization results show that when the weakly polar acetone and the strongly polar solvent DMF reach a ratio of 4:6, the pure PVDF film possesses high piezoelectricity (d₃₃∼ -44.8 pC N^-1) and strong self-polarization. Additionally, the A₄D₆device exhibits high sensitivity (S₁= 0.182 V/N, 0.5 N ∼ 30 N), driven capability (0.49 mW m^-2), and reliability during the electrical tests as a pressure device. This work provides an effective and cost-effective route of optimizing the solvent's polarity to improve the piezoelectric characteristics of the polymer.