SPECTROELECTROCHEMICAL STUDIES OF PROTON-EXCHANGE PROCESSES IN THE ELECTROCHEMICAL REACTIONS OF POLYANILINE USING PH INDICATORS

The thin layer transmission Spectroelectrochemical method using pH indicators such as methylviolet has been applied to study the mechanism of proton exchange accompanying the electrode reactions of polyaniline, in aqueous and non-aqueous media. The results obtained for aqueous solutions seem to suggest that after polyaniline oxidation to the first polaron state, a small insertion of protons from the solution occurs. Further oxidation of polyaniline to the bipolaron state does not induce any change in the solution acidity. In the potential range between the first and the second oxidation step no deprotonation of polyaniline occurs. This process starts simultaneously with the second oxidation peak. In non-aqueous media, no proton exchange is observed during the first oxidation step, whereas in the potential range corresponding to the second oxidation step the acidity of the electrolyte solution increases. Protons are strongly bound within the polyaniline matrix. Chronoabsprptometric measurements show that the observed processes are rapid and reversible. These last features may be utilized in the construction of new electrochromic devices. © 1990.