Beyond the melting point annealing of poly(vinylidene fluoride) for enhanced piezoelectric performance

This study investigates the high temperature, beyond the melting point, and high stress, up to 450 MPa, stretch-annealing process of poly(vinylidene fluoride) and its impact on piezoelectric performance. Using this approach, films with moduli up to 11 GPa were fabricated. Contrary to conventional piezoelectric understanding, our results show a significant increase in the in-plane piezoelectric coefficient (e₃₁) and electromechanical coupling coefficient (k₃₁) with the high temperature-stress annealing despite the increased modulus. These films exhibited exceptional piezoelectric performances, with e₃₁ values reaching ∼190 mC m^-2 and k₃₁ values to 0.25, among the highest reported for PVDF. Microstructural analysis suggests the formation of shish-kebab structures, highlighting the potential for microstructure engineering to enhance piezoelectric performance. These findings have implications for the future development of high-performance piezoelectric polymers.