PREPARATION AND ELECTROCHEMICAL-BEHAVIOR OF CONDUCTING FILMS OBTAINED BY ELECTROPOLYMERIZATION OF BENZIDINE IN AQUEOUS-MEDIA

The electrochemical oxidation of benzidine to obtain an electroactive film of polybenzidine (poly-Bz) is reported. The yield of the electropolymerization reaction depends on temperature and pH in a way that indicates that there is a competitive reaction to film formation. A mechanism that explains these effects and that is used to calculate the rate coefficients of early stages of the process is proposed. The voltammograms of poly-Bz are highly asymmetric, suggesting a complex redox behavior. This film shows thin-layer behavior at sweep rates lower than 0.100 V s(-1), while at higher rates semi-infinite diffusion behavior is observed. Poly-Bz exhibits electrochromic behavior. It is colorless in the reduced state and blue in the oxidized state. Spectroelectrochemical studies on an indium tin oxide electrode show that, upon oxidation, an absorption band with a maximum at 560 nm develops and a well-defined isosbestic point is observed at 415 nm. The variation of the absorbance at 540 nm on the potential shows that the poly-Bz film has a Nernstian behavior with interaction between active sites.