Catalytic synthesis of conductive polypyrrole using iron (III) catalyst and molecular oxygen

The catalytic oxidative polymerization of pyrrole was developed by the use of a relatively small amount of iron(III) salts as a catalyst and molecular oxygen as an oxidant. The reaction rate depended on the solvent used. Thus, the organic solvent with high dielectric constant gave the polymer with high electroconductivity at high yield. In contrast, both the polymerization rate and the conductivity of the produced polymer were low when the solvent with low dielectric constant was used. When propylene carbonate was used as the solvent with high dielectric constant, the turnover number reached about 10 in 96 h based on the charged amount of catalyst, and the highest electroconductivity around 10−2 S cm−1 was achieved without extra doping. The addition of the quaternary ammonium salt to the reaction mixture improved the conductivity. Results on cyclic voltammetry suggested that the redox potential of iron ions depending on the solvent is an important factor to determine the efficiency of the catalytic polymerization of pyrrole.