The development of polymer nanocomposites with enhanced electrical and dielectric properties has attracted significant attention due to their wide-ranging applications in super capacitors, dielectric capacitors, energy storage, and energy density enhancement. This review critically examines the role of nanoscale fillers in enhancing the electrical performance of polymer matrices, emphasizing mechanisms such as interfacial polarization (WPS–ZnO–Kaolin interfaces), formation of percolative conductive networks (rGO network), rGO demonstrate exceptional conductivity and strong synergistic effects, particularly in hybrid configurations, enabling substantial improvements at low filler loadings, Semiconductor-assisted transport (ZnO), metal oxide nanoparticles, such as ZnO, further contribute by modulating crystallinity, narrowing band gaps, and enhancing charge-carrier mobility. Despite these advancements, concerns regarding environmental sustainability, the toxicity of certain nanofillers, and the non-recyclability of conventional thermosetting polymers remain critical challenges. In this context, the incorporation of eco-friendly, naturally abundant materials such as kaolin for morphological control (Kaolin dispersion) alongside the valorization of waste polymers like polystyrene (WPS), presents a promising pathway toward sustainable material design. However, persistent challenges related to filler dispersion, interfacial compatibility, and the trade-off between electrical performance and environmental safety must be addressed. Importantly, this review identifies a significant research gap in the development of hybrid systems combining WPS, ZnO, rGO, and kaolin. Such a composite is expected to exhibit synergistic electrical behavior arising from the interplay between the insulating polymer matrix, semiconducting ZnO, highly conductive rGO, and layered aluminosilicate kaolin. The resulting enhancements are likely governed by percolation effects, interfacial polarization, semiconductor assisted transport and morphological control. Future research should therefore prioritize green synthesis strategies, non-toxic filler selection, and scalable fabrication methods to enable the practical deployment of sustainable polymer nanocomposites in advanced technological applications while minimizing environmental and health risks.
Sallau et al. (Sun,) studied this question.