MECHANISTIC STUDIES OF ELECTROCHEMICALLY DEPOSITED POLY(O-ANISIDINE) FILMS

Electrochemically deposited poly(o-anisidine) films exhibit a,transiti on from insulating pernigraniline to conducting emeraldine salt phase by decreasing the pH of solution from 4.13 to -0.21 as observed from t he optical spectra. A further decrease in pH does not affect the polym erization process. The sheet resistance of the substrate also has a re markable 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 responsi ble for the voltammetric features. The polymerization mechanism mainly involves -NH3+ cationic coupling through preceeding chemical reaction s. Thermograms exhibit a three-step decomposition pattern with large d ifferences in the weight loss of individual steps. The final decomposi tion temperature of polymer varies with the pH of electrolyte solution , indicating the formation of different types of species during deposi tion.