Conducting polypyrrole and polypyrrole/manganese dioxide composites prepared with a solid sacrificial oxidant of pyrrole

Abstract

Polypyrrole was prepared by the oxidation of pyrrole with solid manganese dioxide. The present study concerns the chemistry of this process rather than materials properties of the products. The oxidant alone is insoluble in aqueous medium but the reductive dissolution takes place in the presence of pyrrole. Polypyrrole is the exclusive product below the stoichiometric mole ratio [MnO2]/[pyrrole] = 1.25, and polypyrrole/manganese dioxide composites result at higher ratios. Unlike with iron(III) chloride where protons are generated during the oxidation of pyrrole, with manganese dioxide they are consumed and water is a by-product. The sufficient acidity of the reaction medium is thus needed in order to obtain conducting materials. The presence of organic dyes in the preparation of polypyrrole improved the conductivity. One-dimensional morphology of polypyrrole was observed when methyl orange was introduced to the reaction mixture.