Polyaniline/chloroplatinic acid (PANI/H2PtCl6.H2O) composite is synthesized via in situ oxidative polymerization method. Fourier transform infrared, ultraviolet-visible, energy-dispersive X-ray, and Thermogravimetric techniques are used for the characterization studies. The surface morphology of the samples is investigated by scanning electron microscopy and atomic force microscopy. Dielectric measurements are carried out depending on the temperature. The dispersion process increases the thermal degradation temperature of PANI by about 60 degrees C, while reducing the optical energy gap of PANI from 1.99 to 1.76 eV. Chloroplatinic acid significantly increases the agglomeration and grain size (up to 10 mu m) on the surface of the PANI. Gas sensor measurements show that Polyaniline/chloroplatinic acid composite can be a candidate for ethanol detection. With the dispersion process, the electrical conductivity of PANI increases almost 2.5 times. The charge transport mechanism of the samples is consistent with electron tunneling model up to 97 degrees C and with small polaron tunneling model at higher temperatures. The hopping distance of the charge carriers reduced to 4.82 from 5.30 nm with dispersion process. Experimental results reveal that PANI/chloroplatinic acid composite can be a rather suitable multifunctional material for various applications such as gas sensors, optoelectronic and semiconductor devices. POLYM. ENG. SCI., 59:66-73, 2019. (c) 2018 Society of Plastics Engineers