Redox processes in polyaniline thin films studied by optical multichannel analysis

摘要

Abstract: Optical multichannel analysis (OMA) was used to follow the kinetics of color changes in electrochromic polyaniline (PANI) films when they are polarized in an electrolytic medium at different potentials; these color changes which are related to the transition from one polymer form to another one are very fast. For the setting of electrochromic devices, PANI must be used in acid electrolytic media. In these media, the color change mechanisms are essentially related to the chains protonation/deprotonation. The study is now extended to different pH media (neutral and alkaline) in order to obtain a better understanding of the chemical mechanisms of passage from one form to another one, and particularly of the oxidation of phenyl in quinone rings. OMA allowed us to also obtain an apparent value of the films absorption coefficient. In the investigated range (300/800 nm), several absorption phenomena characteristic of the different polymer forms can be displayed. The range in which two different forms coexist can then be characterized by the deconvolution of the optical spectra. Finally, the electrochromism in polymer is characterized by the change of optical density $Delta@DO directly obtained from the OMA experimental spectra. !25