Tailoring dielectric properties and crystallinity in poly(vinylidene fluoride-co-hexafluoropropylene) nanocomposites via iron (III) chloride hexahydrate incorporation

Abstract

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.