AN ELECTROCHEMICAL STUDY OF PYRROLE N-METHYLPYRROLE COPOLYMER

Electrochemical growth of polypyrrole (PPy), poly-N-methylpyrrole (PMePy) and PPy + PMePy copolymers in 0.5 M LiClO4 + propylene carbonate was studied. The potential of the polymerization threshold increases with decreasing monomer concentration. Composition and redox properties of thin polymeric films were controlled by varying the polymerization potential in a narrow interval between the polymerization and overoxidation thresholds. Virgin copolymers grown from "dry" electrolytes (approximately 10 ppm H2O) show two separate reduction peaks; copolymers grown from water-containing (1 vol.%) electrolytes show a single reduction peak. A correlation between the voltammetric peak potential and the available coulombic capacity of the copolymer was found. An increased [MePy]/[Py] ratio in the copolymer shifts the peak potential to more positive values but the reversible coulombic capacity decreases. Consequently, PPy + PMePy copolymer electrodes do not offer an increased energy density in batteries.