Electroactive bilayers employing conducting polymers. Part 2.—Speciation by in situ spectroscopy

Abstract

Electrochemically driven charge trapping and untrapping reactions in polybithiophene/polyxylylviologen (PBT/PXV) bilayers have been studied using in situ transmission spectroscopy in the visible region. Charge transfer to the outer film is exclusively mediated by the conducting states of the inner film. The redox composition of the outer film was determined as a function of potential and injected charge in cyclic voltammetric experiments. During reduction of the outer film, the semi-reduced PXV⁺ species is the predominant product until essentially all the reactant PXV²⁺ is consumed. Production of fully reduced PXV⁰ depends on film thickness and voltage scan rate. Similarly, PXV⁺ is the predominant product of PBT⁺-mediated PXV⁰ oxidation, until PXV⁰ consumption is almost complete. Slow changes in the outer-film composition due to reaction with trace oxidant (presumed oxygen) in solution were detected.