It is shown that electrochemical cycling of polyaniline modified electrodes in acidic electrolytes containing dissolved catechol(s) results in covalent attachement of this species to polyaniline. Electrochemical properties of polyaniline are significantly altered and a new voltammetric peaks appear that are not assigned to parent polyaniline nor catechol (Fig 1).

Fig. 1. Cyclic voltammogram of catechol-restructured polyaniline film in 0.1M H₂SO₄

The proposed mechanism involves nucleophilic addition of polyaniline to oxidized form of catechol (o-quinone). When sulfonated catechol is generated by the oxidation of guaiacol sulfonic acid on polyaniline film it also attaches to the polymer to form a new self-doped composite retaining its electrochemical activity in neutral electrolytes. Morover it exhibits persistent electrochemical activity toward the oxidation of ascorbic acid.

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