Role of film history and observational timescale on redox switching kinetics of electroactive films. Part 1.—A new model for permselective films with polymer relaxation processes

Abstract

A model involving the transport of mobile species and film structure relaxation processes is developed for redox switching of permselective electroactive polymer films. Free-energy profiles for such systems show that a variety of pseudo-equilibrium (metastable) states may be populated. The initial polymer film state is determined by the film's history. The participation of solvent transfer and polymer reconfiguration depend on the experimental timescale. The model considers electron/counter-ion transfer, solvent transfer and polymer reconfiguration as distinguishable processes. Redox switching involving these three processes is described by a scheme-of-cubes type formulation. The model is generally applicable to any (electrochemical or non-electrochemical) technique. The model encompasses a variety of observed phenomena including ‘break-in’, charge- and masstrapping, structural evolution with redox cycling, kinetic decoupling of ion and solvent transfer and variation of apparent charge transport rate and formal potential with the experimental timescale.