Electrochemical synthesis of poly(o-anisidine), poly(o-toludine) and their copolymers in organic sulphonic acid

The effect of organic sulphonic acids on electrochemical, optical and conductivity properties of poly(o-anisidine) (POA), poly(o-toluidine) (POT) and poly(o-anisidine-co-o-toluidine) (POA-co-POT) thin films has been investigated. The films were synthesized electrochemically, individual as homopolymers and then combined as (binary copolymer) under cyclic voltammetric conditions in an aqueous solution of sulphuric acid, p-toluene sulphonic acid, sulphamic acid and sulphosalicylic acid at room temperature. The films were electropolymerized in solution containing 0.1 M monomers and respective electrolyte (1 M sulphuric acid or organic sulphonic acid) by applying sequential linear potential scan rate of 50 mV/s between -0.2 and 1.0 V versus Ag/AgCl electrode. The electrosynthesized films were characterized by cyclic voltammetry, UV-Vis spectroscopy and conductivity measurement. It is observed that the UV-Vis peaks for sulphuric acid, p-toluene sulphonic acid, sulphamic acid and sulphosalicylic acid appear in the region of the conducting emeraldine salt (ES) phase. Overall, the polymers prepared using all these three organic sulphonic acids have higher conductivity than sulphuric acid; however, the higher conductivity is observed for p-toluene sulphonic acid as electrolyte in comparison with sulphamic acid and sulphosalicylic acid. The formation of copolymer (POA-co-POT) has been supported and confirmed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) studies. A possible scheme of reaction mechanism for homo- and copolymer has been suggested.