Influence of surface modified TiO₂ nanoparticles on dielectric properties of PVdF–HFP nanocomposites

Polyvinylidene fluoride-co-hexaflouropropylene (PVdF–HFP)/TiO₂ hybrid nanocomposites membranes for electrical applications have been prepared using a solvent casting technique. The interface between PVdF–HFP and TiO₂ was modified using aminopropyltrimethoxysilane (APS) coupling agent. The silane linkages on the TiO₂ surface have been confirmed using Fourier transform infra red spectroscopy. WAXD and DSC analysis has been employed to estimate the variation in crystallinity within the membrane as a function of the incorporation of both untreated and APS treated TiO₂. The dispersion of both nanoparticles in the PVdF–HFP matrix were characterized by atomic force microscopy and differences were observed in the images of APS treated and untreated. Variation in electrical properties such as conductivity, dielectric constant, dielectric loss and electric modulus of the hybrid composite films were studied employing AC impedance spectroscopy over a range of frequency from 1 kHz to 1 MHz at room temperature. Theoretical models like Maxwell, Faruka, Rayleigh and Lichtenecker were employed to calculate the effective dielectric constant of hybrid nanocomposite membranes and the estimated values were compared with the experimental data. Further, the variation in thermal stability of PVdF–HFP membrane as a function of untreated and silane treated TiO₂ reinforcement has been estimated using thermogravimetric analysis.