Studies on Influence of Inorganic Dopants in Presence of Electrolyte on the Conductivity of Polyaniline, Poly(o-Anisidine), and Their Copolymer Thin Films

Abstract

An attempt was made to prepare polyaniline (PA), poly(o-anisidine) (POA), and copolymer polyaniline–poly(o-anisidine) (PA–POA) thin films dopped by several inorganic saltas (sulfates and chlorides) with varying sizes of cations using an aqueous solution of H2SO4 as an electrolyte. Various inorganic salts as dopants, viz., K2SO4, Na2SO4, Li2SO4, MgSO4, KCl, NaCl, LiCl, and MgCl2, were used at room temperature. The films were electropolymerized in solution containing 0.1-M monomer(s), 1-M H2SO4 as electrolyte, and 1-M inorganic salt by applying sequential linear potential scan rate 50 mV/s between −0.2 to 1.0 V vs Ag/AgCl electrode. The electrosynthesized 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 usually appearing at about 810 to 826 nm with a shoulder at 416 to 426 nm, showed a shift in presence of doping salt for the emeraldine salt (ES) phase of PA, POA, PA–POA. In the overall study, a significant increase in conductivity is observed for all dopants mentioned above, and among them K2SO4, is found to be the best in sulfate category and KCl in chloride category.