NUCLEATION, GROWTH AND BRANCHING OF POLYANILINE FROM MICROELECTRODE EXPERIMENTS

The kinetics of electrochemical formation of polyaniline were studied under potentiostatic conditions on gold and platinum microelectrodes. Two different stages of growth were observed, the first corresponding to the formation of a compact layer with average thickness of about 200 nm, the second corresponding to the growth of a branched structure. The initial parts of the current transients obtained at two different aniline concentrations were interpreted by means of the theory for progressive and instantaneous nucleation and growth. The study of the potential dependence at the very initial stage of film formation has shown that nucleation is not likely to be an electrochemical step in the overall polymerization process. A detailed investigation of the growth process alone yielded different apparent transfer coefficients corresponding to the two different stages of growth.