Studies on electrochemically synthesized conducting polymer

Abstract

Polyanilines are prepared by electrochemical oxidative polymerzation of aniline at different bath composition, temperature and current density/The different bath compositions used were: / monomer (aniline) 20 mIll acids: (H2S04! HCI! HCI04) 100 mill Electrochemical depositions were carried out at 5°C, 9°C, 18°C and 25°C on Pt-electrode. The deposition current densities were 5 mA/cm2 , 10 mA!cm2 and 15 mA!cm2 Optimal conditions for the electrosynthesis of polyaniline were also determined. The polymers obtained in this study under different conditions were characterized by IR, X-RD and elemental analysis. The d.c. conductivity and UV-Vis spectroscopy measurements were performed to have an insight in the electrical and optical properties of the studied polyaniline. To determine the nature of conductive polymer, electrical conductivities of the polymer samples were measured at different temperatures. Most of the samples except one (prepared in H2S04 solution) showed their semiconductive behavior i.e. their electrical conductivity increases with the increase of temperature. The only sample prepared in presence of H2S04 showed metallic behavior. Its electrical conductivity decreases with the increase of temperature which is quite peculiar. The resistance of this sample is much lower than those of other samples. In the IR spectra, the band characteristics of aniline confirmed the presence of monomer ring in the polymer. X-ray diffraction patterns of polyaniline showed two peaks at 28 valued around 9° and 12°. The peaks were found diffuse. Relatively better crystallinity was observed in the case of smaller molecular size dopant. The experimental results of elemental analysis were found slightly lower than those of the corresponding theoretical values. UV visible spectra of polyaniline showed the two absorption bands. Bands at around 335nm are due to rc-+ rc* transition. The broader bands at around 500-540nm might be due to n-+ rc* transition. Relatively lower temperature, lO mA/cm2 current density and H2S04 electrolyte are found suitable for the synthesis of better quality of conductive polyaniline.