Synthesis of High-Performance Polyvinylidene Fluoride Composites via Hydroxyl Anchoring Effect and Directional Freeze-Drying Method

Polyvinylidene fluoride (PVDF) and its copolymers present extensive application prospects, especially in the field of wearable electronics. However, utilizing nanofillers for enhanced β-phase and piezoelectric properties faces challenges like noncontinuous interfaces, poor compatibility between nanofillers and PVDF matrix, and the requirement of high-voltage polarization, hindering extensive domain alignment on a large scale. Herein, a method is proposed to synthesize high-performance PVDF composites by introducing hydroxylated barium titanate (H@BTO) nanoparticles and a directional freeze-drying method to enhance β-phase content and piezoelectric properties without polarization. Molecular dynamics simulations reveal robust binding interactions between Ba and F atoms along with OH surface terminations on H@BTO, facilitating hydrogen bonding within the PVDF matrix, resulting in dipole alignment and increased spontaneous polarization. The composite film achieves an 86.69% β phase content and a piezoelectric coefficient of ≈14.49 pm V −1 without electric polarization. The freeze-drying PVDF-H@BTO composite film paired with a PA6 membrane is used to fabricate triboelectric nanogenerator, demonstrating a current density of ≈107.5 mA m − 2 and an output voltage of ≈832 V. Results demonstrate that the utilization of strong binding interactions between various atoms, the hydroxyl anchoring effect, and directional freeze-drying method as a strategy holds promising prospects for synthesizing high-performance piezoelectric composites.