Electrochemistry of quinoid dopants in conducting polymers

Abstract

The preparation and electrochemical properties of polypyrrole (PPy) films, in which sulfonated hydrobenzoquinone, naphtho- and anthraquinone are intercalated as dopants, are described. The redox characteristics of the quinoid dopant are similar to the reported voltammetry of adsorbed quinones. Unlike the limited electroactive coverage of the quinone in non-conducting coatings, the apparent electroactive coverage of the quinoid dopant can be controllably varied, and high electroactive coverage can easily be obtained within a few minutes. PPy/NQS exhibits catalytic oxidation of ascorbic acid, which is controlled by the diffusion of the substrate to the electrode. Catechol derivatives are used as electrocatalysts for the formation of PPy films. A common dependency of the quinone/hydroquinone redox on the solution pH is observed. These phenomena are attributed to changes in the PPy, rather than in the dopant, which may be caused by the low p K a value of the pyrrole ring in the film, pH-dependent structural changes in the films and different interactions of the PPy backbone with the two oxidation states of the quinones.