Mechanism of the biomolecular synthesis of PEDOT:PSS: importance of heme degradation by hydrogen peroxide

The use of biomolecules as oxidants for the synthesis of conducting polymers provides an important tool for the control of polymer properties. Using PEDOT:PSS as a representative conducting polymer, we compare a set of heme proteins (soybean peroxidase, cytochrome c, and horseradish peroxidase) used as oxidants. The resulting PEDOT:PSS was characterized with visible and near IR spectroscopy, Fourier transform infrared spectroscopy, electron spin resonance spectroscopy, and four point probe conductivity measurements. We find that the relative concentrations of bipolarons and polarons vary as a function of the protein used for polymerization. We then show that heme degradation by hydrogen peroxide plays a critical role in determining polymer properties.