Conductivity and dielectric relaxation of cross-linked polyvinyl alcohol reinforced by low amount of zinc oxide

Abstract

This study reports the fabrication of cross-linked Poly(vinyl alcohol)/zinc oxide (XLPVA/ZnO) nanocomposite films with improved thermal and dielectric properties for potential use in flexible electronics and energy storage devices. The motivation lies in developing low-cost, flexible, and thermally stable dielectric materials by combining chemical cross-linking and nanoparticle reinforcement. ZnO nanoparticles were synthesized via a modified sol–gel method and incorporated into the PVA matrix at different weight percentages (x = 0, 1, 2, 4, and 6 wt%), following cross-linking with oxalic acid at a 20% degree. Structural analysis by XRD revealed increase in both crystallinity and crystallite size with increasing ZnO content from 16 to 27 nm. FTIR spectra confirmed successful ZnO incorporation, as evidenced by additional Zn–O vibrational bands at 475, 553, 578–579, and 670 cm⁻¹. Thermogravimetric analysis (TGA) showed improved thermal stability, with residual mass increasing from ~ 10% (x = 0 Wt%) to ~ 16% (x = 6 wt%). Dynamic mechanical analysis (DMA) revealed significant shifts in the α-relaxation peaks, observed at 40 °C/65 °C and 46 °C/71 °C for 4% and 6% ZnO, respectively, indicating reduced chain mobility due to polymer-filler interactions. Dielectric measurements (40 Hz–1 MHz) confirmed the disordered nature of the system, with AC conductivity following Jonscher’s power law. Activation energy values extracted from Arrhenius plots remained below 1 eV, consistent with ionic conduction. Modulus formalism further identified a thermally activated relaxation process, confirming localized charge carrier dynamics. These results highlight the dual role of cross-linking and nanoparticle addition in tuning the dielectric and thermal response of PVA-based composites. The materials developed here present promising features for scalable integration into future flexible, low-cost dielectric components, and embedded sensor technologies.