A new method for incorporation of nitroxyl radicals into the polypyrrole matrix

In presence of protons nitroxyl radicals (NR) cause polymerization of pyrrole (Py) to polypyrrole (PPy) with incorporated reduced (hydroxylamine) form and oxidized (nitrosonium ion) form of nitroxyl radical in polymer matrix. In electrochemical oxidation of pyrrole in the presence of NR a coupled electrochemical-chemical (ECH-CH) synthesis produces PPy films with incorporated nitrosonium ions. They can be reduced to NR by partial film reduction. The pattern of polymer ESR signal strongly depends on the extent of film reduction and reflects the ratio of NR and polaron concentrations. The type and the chain length of soluble pyrrole oligomers accumulated in the solution during the chemical or ECH-CH oxidation of pyrrole by NR strongly depend on the experimental conditions. At least two different radical species have been identified in the reaction mixture using UV-Vis-NIR and ESR spectroscopy.