Synthesis, characterization and comparative analysis of poly(aniline-co–o-methoxy aniline) with polyaniline and poly(o-methoxy aniline) coatings on copper

In this paper the Poly (aniline-co–o-methoxy aniline) (PAOMA) copolymer coatings, as well polyaniline (PANI) and poly (o-methoxy aniline) (POMA) individual polymer coatings, were synthesized on copper (Cu) substrates from an aqueous solution of sodium salicylate. A series of PAOMA copolymer coatings were deposited by electrochemical copolymerization of aniline (ANI) with o-methoxy aniline (OMA) using different monomer feed ratios under cyclic voltammetric conditions. A comparative analysis of the cyclic voltammograms (CVs) recorded during polymerization of aniline, o-methoxy aniline, and their copolymer clearly reveals the effect of the monomer ratio on the formation of the copolymer, polymer, and the quality of the coatings. All the resulting coatings were characterized by cyclic voltammetry, UV–visible absorption spectroscopy, scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The synthesis of the copolymer, using a mixture of monomers in the aqueous sodium salicylate solution, was confirmed through a comparative study of the results obtained from the polymerizations, as well with the characterizations of the individual monomers, aniline and o-methoxy aniline. Corrosion resistant characteristics of resulting coatings were evaluated by potentiodynamic polarization measurement in aqueous solution of 3% NaCl solution. It extracts the values of corrosion potential (E_corr), corrosion rate (CR), porosity (P) and protection efficiency (%PE). The analysis of these results imply that the copolymer PAMOA-5 coating provides effective protection to Cu against corrosion in aqueous 3% NaCl as compared to that of the other copolymers and also than the corresponding homopolymers. For PAOMA-5 coated Cu it was found that the remarkable positive shift of 344 mV in E_corr, substantial reduction in corrosion rate 875 times lower than that observed for bare Cu, lowest value of porosity (0.44 × 10^–6) and highest protection efficiency of 99.9%.