Electroactive polyaniline (PANI) films were made in aqueous solutions at pH 2 to 12 by means of potential cycling. The protonation degree of oligoanilines and PANI was low in solutions of high pH, resulting in high polymerization efficiency. Fewer PANI hydrolysis products were formed when electropolymerization of aniline was conducted in neutral or slightly basic solutions, providing a synthetic route for PANI with little degradation. FT-IR spectra of PANI made in solutions of different pH displayed main vibrational bands of the polymer, including the characteristic peak of protonated states of PANI. SEM images of films made in neutral or basic solutions showed three-dimensional distributions, which were very different from those made in slightly acidic solutions. (c) 2005 Springer Science + Business Media, Inc.