GROWTH OF POLYANILINE FILMS UNDER PULSE POTENTIOSTATIC CONDITIONS

Strong activation of the growth of polyaniline (PANI) films is found to occur when a pulse potential programme consisting of periodic cathodic and anodic rectangular pulses is applied. The potential interval for the cathodic pulses where growth activation is observed coincides with the potential interval where the polymerized material is almost fully reduced but is still conducting. It is found that the pulse programme does not influence the formation of the first nuclei but markedly affects the early stage of growth of the PANI films, i.e. the stage where different processes such as oligomerization, further nucleation and growth up to the formation of a full coverage layer take place on the electrode surface. The further growth of the compact PANI layer seems to be unaffected by the pulse procedure. It is shown that the activated polymer growth should not be related to the influence of the pulse procedure on the overoxidation (termination) reaction of the polymer chains. Different reasons for the activated PANI growth observed under pulse conditions, such as continuous redistribution of the redox centres in the PANI nuclei, periodic stretching and relaxing of the polymer chains etc., are discussed briefly.