Source dependence of polyacrylonitrile electrospun nanofibers on piezoelectric response

Abstract

Electrospun polyacrylonitrile (PAN) nanofibers exhibit exceptional piezoelectric properties, positioning them as promising candidates for applications in energy harvesting, mechanical sensing, acoustic detection, and advanced wearable electronics. However, inconsistencies in reported piezoelectric properties across studies have hindered the advancement of this field. This study systematically elucidates source-dependent piezoelectric heterogeneity in electrospun PAN nanofibers through multiscale structural and compositional analysis. Five commercial PANs were selected and processed into nanofiber membranes of similar diameter and thickness by an electrospinning technique. The nanofibers were then subjected to a series of characterizations, including GPC, FTIR, NMR, XPS and XRD, dielectric properties, water contact angle and tensile properties, in addition to piezoelectric properties. Our experimental results exhibited significant variations in piezoelectric performance between the nanofibers produced from different PAN sources. When subjected to identical impact conditions, the piezoelectric responses exhibited a 4.6-fold discrepancy in open circuit voltage and a 15-fold discrepancy in electrical power output. Key determinants of piezoelectric performance variability were found to be molecular architecture, copolymer composition (methyl acrylate/vinyl acetate: 0.1–0.87 wt%), and ionic impurity profiles (e.g. NH₄⁺ from radical initiator decomposition). These result in varying degrees of planar zigzag conformation (Φ = 50.4–66.1%). Acrylonitrile with >98% in the molecule maintained optimal dipole orientation despite trace comonomers. Comonomer incorporation greater than 2 wt% induced lattice distortion and d₁₀₀ spacing expansion and decreased piezoelectricity despite the high ionic impurity content. Ionic modulation at concentrations (0.37–0.72%) improves piezoelectric performance. The dielectric permittivity remained almost unchanged throughout the nanofiber from different PAN sources. These results establish a predictive structure–property framework for industrial feedstock screening, performance prediction, and targeted molecular engineering of PAN-based piezoelectric systems.