Voltammetric and in situ FTIRS study of the electropolymerization of o-aminobenzoic acid at gold and graphite carbon electrodes: influence of pH on the electrochemical behaviour of polymer films

摘要

The electrochemical homopolymerization of o-aminobenzoic acid has been performed on both gold and graphite surfaces in perchloric acid aqueous medium by cyclic scanning of the potential. Electroactive polymeric materials are formed in all cases but the amount of electropolymerization products seems to be increased by the graphite carbon electrodes. The polymers obtained have been characterized electrochemically. In addition, in situ FT-IR spectroscopy and scanning electron microscopy were combined to study the redox behaviour of the oxidation products and the surface morphology of the coatings. Characteristic absorption features related with benzenoid and quinoid rings and different types of C–N bonds point to the operation of redox processes similar to those undergone by the parent compound polyaniline. Owing to the presence of the –COOH group in the carbon backbone, polymer films obtained from o-aminobenzoic are, contrary to polyaniline, electroactive at pH values over 3. Besides, it was observedthat repeated oxidation–reduction cycles in working solutions with pH above 6 led to the dissolution of the deposited material.