Oxidation-reduction interactions between electroactive polymer thin films and Au(III) ions in acid solutions

Polyaniline (PAN) and polypyrrole (PPY) were coated on pristine and acrylic acid graft copolymerized low-density polyethylene (LDPE) films and exposed to chloroauric acid solutions. The reduction of Au(III) ions in solution was followed using ultraviolet-visible absorption spectroscopy. The structures of the PAN and PPY films after varying periods of immersion in the chloroauric acid solutions were analyzed using ultraviolet-visible absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). In the process of reducing Au(III) to Au(0), the electroactive polymers underwent degradation, evidenced by a gradual decrease in electrical conductivity, ring substitution by chlorine, and a loss of material into solution. The degradation is due to the higher propensity of the polymers when existing in a higher oxidation state to undergo hydrolysis reactions to soluble products.