MORPHOLOGY AND GROWTH-RATE OF POLYANILINE FILMS MODIFIED BY SURFACTANTS AND POLYELECTROLYTES

The rate of electropolymerization of aniline can be significantly accelerated by the addition of small amounts of bifunctional species, polyelectrolytes or surfactants to the monomer solution. In the first case, using para-phenylene diamine (PPDA) for example, the morphology of the polyaniline (PANI) film is densely branched and fibrous. In the latter cases, the mechanism of growth enhancement appears to be quite different, controlled by physical rather than chemical processes. Scanning electron micrographs reveal that the typical fibrous PANI morphology is suppressed and that the granular structure of the initial nucleation is maintained. Cyclic voltammetry confirms that these modified aniline polymers still demonstrate the electrochemical behavior characteristic of pure PANI. Elemental analysis by X-ray photoelectron spectroscopy (XPS) shows that, based on sulfur-to-nitrogen (S/N) ratios, some of the polyelectrolyte or surfactant additive is incorporated into the polymer surface depending on the initial relative concentrations. A model of the effect of polyelectrolyte or surfactant during the electropolymerization of aniline is presented.