The influence of electrolyte pH on the surface morphology of polypyrrole

Cyclic voltammetric studies of the aqueous synthesis of polypyrrole (PPy) with p-toluenesulfonic acid (pTSA) supporting electrolyte over a range of pH values, from pH 4 to pH 11, have been made. The optimum system pH for the p-toluene sulfonate (pTS) dopant anion is approximately 11. Synthesis of polypyrroles in electrolytic systems with a pH in the optimum region has been observed to produce a more uniform surface morphology with fewer and smaller surface defects. Electrolytic systems with pH values less than the optimum suffer from mixed oxidation mechanisms. The oxidation of the pyrrole monomer was found to compete with the oxidation of water to evolve O 2(g), which adsorbs at the anode/polymerization surface to act as a nucleation or polymerization focal point. The resultant polymer morphology is irregular with large cup- or bell-like surface defects due to gas adsorption.