Hydrophobic modification of kaolinite by coating with the conductive polythiophene and investigation of the usability as the environmental-based sensors

Abstract

To prepare an electrically conductive clay-composite, in this work, the surface of kaolinite plates was covered with the hydrophobic polythiophene (PTh) nanoparticles, through in-situ oxidative polymerization of thiophene in an organic solvent mixture. By changing the polymerization conditions such as types of solvents used as polymerization media, volume ratios of the solvents in the mixture, and mole ratios of the oxidant/monomer, the composite with the highest conductivity (7.95 × 10–5 S cm−1) was obtained. Depending on the polythiophene (PTh) content (%) of the composite, Vickers microhardness, elastic modulus, Brunauer, Emmett, and Teller (BET) analysis, wet particle size distribution, and water contact angle measurements were performed. It was observed that the hydrophilic nature of kaolinite remarkably altered after the incorporation of PTh particles. FTIR, XRD, TGA, and SEM–EDX techniques were also used for the characterization of the composite. The performance of the composite in the environmental-based sensors, including humidity and temperature sensing, were examined, and the resistance values of the composite exhibited quite stable and reproducible responses, especially to the temperature changes, between 1 and 120 °C compared to the pure PTh.