Investigation of Polymer-Dopant Interactions at Polyaniline-Modified Electrodes: In Situ Analysis by FTIR Spectroscopy

The electrochemical response of electrodeposited polyaniline is shown to depend strongly upon the pH of the deposition solution. The concentration of anion present during deposition has only a weak effect. When the pH of the deposition solution is less than 1.0, the response is typical of the para-substituted phenyleneamineimine structure. When the pH of the deposition solution is greater than 1.0, an additional voltammetric wave appears, and the response is a function of the dopant anion. Infrared spectroscopy was used to examine the structural properties of these films directly in situ. While films that displayed voltammetry typical of the para-substituted compound decomposed to form p-benzoquinone at high positive potentials, films displaying atypical voltammetry did not show evidence of p-benzoquinone decomposition products. Spectral analysis indicates that cross-linked structures may be important in determining the anion-dependent voltammetric response. Further, investigations into the nature of bonding in the polymer-dopant complex revealed a weak ionic interaction.