Positive temperature coefficient of resistance in Na2S interacted polyaniline on cellulose substrate: A flexible electronic material

Flexible electronic materials of polyaniline (PANI) chemically interacted with Na2S have been developed with the objective of improving and tuning its electrical transport properties and optical properties. The chemical interaction of Na2S with PANI was realized by the synthesis process of physical vapor polymerization of aniline over cellulose substrate. The prepared samples of PANI interacted with Na2S at different concentrations (3%, 5%, 7%, and 10%) have been studied through X-ray diffraction (XRD) measurement, scanning electron microscope (SEM) measurement, analysis of FTIR spectra, I-V measurement, and analysis of UV–vis–NIR absorption spectra. From XRD measurement it was observed that the peaks corresponding to the emeraldine form of PANI were obtained during polymerization, which is electrically conductive. Being partially polymerized, this form of PANI provides the scope for further functionalization through chemical interaction with Na2S. As a consequence of chemical interaction with Na2S, its resistivity was found to increase systematically with the increase of concentration of Na2S. A twelve times change in resistivity was recorded with Na2S interaction. The temperature dependence of electrical conductivity shows an excellent positive temperature coefficient of resistance, which is of profound technological significance for self-controlled overheating protection of electronic devices.