Exploration of the electrical and dielectric behaviours of DGEBA/PPy-doped TiO 2 composites: Insights from AC impedance spectroscopy

Abstract

This study investigates the electrical and dielectric properties of nanocomposites based on diglycidyl ether of bisphenol A (DGEBA) epoxy resin reinforced with polypyrole-doped titanium dioxide (PPy-doped TiO₂) nanoparticles. A key finding is the identification of a percolation threshold at approximately 3 wt%, indicating the formation of a conductive network within the insulating polymer matrix. AC conductivity measurements, performed over the frequency range 100 Hz–1 MHz and temperatures range 300–400 K, show that the conductivity spectra obey Jonscher’s power law and align with the non-overlapping small polaron tunneling (NSPT) conduction mechanism. Two dielectric relaxations, α-relaxation and Maxwell–Wagner–Sillars (MWS) polarization, were observed in the electric modulus spectra and successfully fitted using the Havriliak-Negami model, highlighting the influence of nanoparticle dispersion on segmental dynamics and interfacial polarization. Importantly, the analysis of relaxation parameters indicates that increasing PPy-doped TiO₂ content enhances charge carrier mobility and interfacial polarization. Activation energies, derived from the temperature dependence of relaxation time and DC conductivity, further confirm the significant impact of nanoparticle incorporation on the conduction processes within the nanocomposite system.