Morphology of electrochemically prepared polyaniline. Influence of polymerization parameters

The kinetics of electrochemical aniline polymerization in aqueous acidic solutions have been investigated by chronocoulometry as a function of the electrolyte anion (i.e. HSO4–, Cl–, NO3–, ClO4–, CF3CO2–), concentration of aniline and para-phenylenediamine (PPDA) as an additive and also in terms of potential or current parameters during film preparation. The morphology of the resulting films was examined by scanning electron microscopy and by porosity measurements. Porosity values were determined based on film thicknesses (40–2000 µm) of polyaniline (PANI) layers saturated with electrolyte solution. While the standard recipes for electrochemical aniline polymerization yield films of porosities P>90%, much denser films (P≈60%) were prepared from aqueous solutions of 0.5 mol dm–3 aniline in 1.0 mol dm–3 HClO4 in the presence of 25 mmol dm–3 PPDA. The results are discussed in terms of a qualitative model for film growth and in view of potential applications in batteries.