Tailoring Dielectric Properties and Crystallinity in Poly(Vinylidene Fluoride-Co-Hexafluoropropylene) Nanocomposites via Iron (III) Chloride Hexahydrate Incorporation

This study investigates the impact of iron (III) chloride hexahydrate (FeCl3·6H2O) incorporation on the structural, thermal, and dielectric properties of poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)] nanocomposites, which were prepared using a solution casting method with varying filler concentrations (1–4 wt%). Scanning electron microscopy revealed a systematic increase in porosity—from 0.72% in pure P(VDF-HFP) to 27.5% at 4 wt% FeCl3·6H2O—along with increased pore size and surface heterogeneity. Atomic force microscopy confirmed enhanced surface roughness correlating with increased filler content. Fourier-transform infrared spectroscopy demonstrated a significant α-to-β phase transformation, indicating the formation of the polar β-phase with increasing FeCl3·6H2O content. X-ray diffraction analysis corroborated these findings, revealing a notable increase in crystallinity and β-phase content, with 4 wt% FeCl3·6H2O achieving the highest β-phase fraction (88.99%). Thermogravimetric analysis confirmed thermal stability up to approximately 500 °C, with a gradual shift in degradation onset attributed to FeCl3·6H2O interactions. Dielectric measurements at 10 Hz showed a remarkable enhancement in dielectric constant—from 5.62 in pure P(VDF-HFP) to 19.16 at 4 wt% FeCl3·6H2O—while maintaining a low dielectric loss (< 0.30). These improvements are attributed to the synergistic effects of FeCl3·6H2O on porosity, phase transformation, crystallinity, thermal stability, and dielectric properties. The superior performance of these nanocomposites makes them promising candidates for flexible electronics, energy storage systems, and advanced sensors.