Electrochemical and chromogenic relaxation processes in polyaniline films

One critical feature for practical applications of polyaniline (PAni) in electrochromic devices is the rate of color change when an electric perturbation is applied. The electrochemical and chromogenic reactions of PAni were quantified running chronoamperometric experiments coupled to spectrophotometry in the visible region. It was verified that the process of color change does not follow the charge injection, depending on the sweep rate and also if the process is oxidation or reduction. It was shown that the reduction and oxidation processes have different kinetics, mainly related to the different polymer conformations in both redox states and it was also shown that the chromogenic process must be related to conformational changes produced by the transformation of benzenoid to quinoid character and these changes are slower than the injection charge.