Novel piezoelectric properties of electrospun polyamide-imide nanofiber membranes

Abstract

Electrospinning is an efficient method for generating piezoelectric nanofiber membranes. However, the majority of piezoelectric nanofibers are derived from a limited pool of polymer sources, such as polyvinylidene fluoride, polyacrylonitrile, poly(L-lactic acid), and nylon-11, which restricts the exploration of piezoelectric properties from other polymer nanofibers. This study presents the first-ever investigation into the piezoelectricity of electrospun polyamide-imide (PAI) nanofibers, paving the way for the development of novel functional materials. We discovered that a PAI nanofiber membrane (with a size of 2 × 2 cm² and a thickness of 100 μm) subjected to compressive impacts (force of 8 N, frequency of 2 Hz) yielded an open-circuit peak-to-peak piezoelectric voltage (V_p–p) of 17.17 ± 0.32 V and a short-circuit peak-to-peak current output (I_p–p) of 0.35 ± 0.02 μA. More significantly, this piezoelectric nanofiber membrane demonstrated exceptional thermal resistance, with a piezoelectric charge coefficient (d₃₃) as high as 116 pC N⁻¹ at room temperature, and a d₃₃ of 97 pC N⁻¹ at 220 °C. This high-temperature resistance performance surpasses that of most reported piezoelectric polymers. Additionally, molecular modeling results suggest that the presence of a net dipole moment in the vertical direction of straight PAI molecular chains enables the formation of a net large dipole in the thickness direction of the nanofiber membrane, thereby accounting for its piezoelectric properties. Electrospun PAI nanofiber membranes may constitute a novel piezoelectric material suitable for high-temperature energy harvesting and sensing applications.