Mechanistic studies of electrochemically deposited poly(o-anisidine) films

Abstract

Electrochemically deposited poly(o-anisidine) films exhibit a transition from insulating pernigraniline to conducting emeraldine salt phase by decreasing the pH of solution from 4.13 to -0.21 as observed from the optical spectra. A further decrease in pH does not affect the polymerization process. The sheet resistance of the substrate also has a remarkable influence in terms of rate and selectivity in the deposition of a particular phase. Morphological investigations indicate a change from a granular to a fibrillar type pattern with decrease in pH from 4.13 to -0.55. The substrate resistance and pH of solution are responsible for the voltammetric features. The polymerization mechanism mainly involves -NH₃⁺ cationic coupling through preceeding chemical reactions. Thermograms exhibit a three-step decomposition pattern with large differences in the weight loss of individual steps. The final decomposition temperature of polymer varies with the pH of electrolyte solution, indicating the formation of different types of species during deposition.