Characterization of poly(pyrroles) by cyclic voltammetry

Abstract

Redox voltammetry provides a means to distinguish between poly(pyrroles) that appear similar in many other respects. Under a consistent set of experimental conditions, poly(pyrroles) doped with various small mobile anions (exemplified by tetrafluoroborate, BF₄^–) gave broad reduction waves at facile potentials, whereas poly(pyrroles) doped with several larger and less-mobile anions (exemplified by p-toluenesulfonate, PTS) gave strikingly sharp reduction waves at markedly more cathodic potentials. This distinction appears intrinsic to the different materials and alteration of polymer preparation conditions failed to convert BF₄^–-type behaviour to PTS-type behaviour. In contrast, the reverse switch was achieved, but only under the extreme preparation conditions of low monomer concentration which yielded poor quality film morphology. However, benzenesulfonate-doped poly(pyrrole) was more readily switched between the two types of redox behaviour depending on the polymerization solvent, this result offering opportunity for manipulation of redox properties, with implications for redox-based applications of these materials.