Influence of inorganic salts as dopants in the presence of electrolyte on the conductivity of poly[aniline-co-(o-anisidine)-co-(o-toluidine)] thin films

An attempt has been made to prepare poly [aniline-co-(o-anisidine)-co-(o-toluidine)] (PA-co-POA-co-POT) thin films doped by several inorganic salts (sulphates and chlorides) with varying size of cations using aqueous solution of H2SO4 as electrolyte. Effect of dopants in the presence of electrolyte is rarely studied in the field of conducting polymer. Various inorganic salts, viz., K2SO4, Na2SO4, Li2SO4, MgSO4, KCl, NaCl, LiCl and MgCl2, are used as dopants at room temperature. The films were electropolymerized in solution containing 0.1 M monomer(s), 1 M H2SO4 as electrolyte and I M inorganic salt by applying a sequential linear potential scan rate of 50 mV/s between -0.2 and 1.0 V versus Ag/AgCl electrode. The electro-synthesized films were characterized by cyclic voltammetry, UV-visible spectroscopy and conductivity measurements using a four-probe technique. It was observed that the UV-visible peaks are appearing at about 816 nm with a shoulder at 420 nm for the emeraldine salt (ES) phase of PA-co-POA-co-POT without any doping salt. In the presence of salts, a shift for these absorption spectra is observed to lower wavelength in between 768 and 802 nm, however, a shift of shoulder to higher wavelength at 440 nm. In overall study, an increase in conductivity is observed for all dopants mentioned above and amongst these K2SO4 is found to be the best among sulphates and KCl among chlorides.