Organic Electrochemistry in the Solid State‐Overoxidation of Polypyrrole

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Abstract
Anodic overoxidation of polypyrrole in the presence of nucleophiles such as H2O, OH−, CH3OH, CH3O−, Br− and CN− has been studied in detail. At potentials up to 2.1 V (vs. SCE), irreversible anodic peaks are observed with 200 nm layers on Pt. In most of the cases, a total of z = 4 – 6 F/mol monomer unit initially oxidized in the reversible potential region to the radical cation has been evaluated. Only every third ring is involved by this way. Characteristic products in aqueous systems are pyrrolinones (with a keto group in 3‐position), z = 4, and the product of further hydroxylation in 4‐position (z = 6). In the presence of the other nucleophiles, corresponding substitution products seem to be generated. The central reactive intermediate seems to be the dication. Pronounced deviations from this scheme, which is confirmed by IRRAS results, seem to proceed in the presence of strong nucleophiles as OH−, which add initially to the radical cation, and upon strong polarization, which may lead to an attack of the other rings and/or polymer destruction. Practical implications are due to polymer modification and battery material optimization.