Theory for solvent and salt transfer accompanying redox switching of electroactive polymers under permselective and non-permselective conditions: Part 1. - Complete redox switching

We present a thermodynamic treatment of ion and solvent transfer processes that accompany redox switching of an electroactive polymer under permselective and non-permselective conditions. A comprehensive model for solvent and salt transfer in polymers with different charge types is developed for the ‘end-to-end’ redox switching (complete oxidized/reduced interconversion) process. In this model during the redox reaction, an arbitrary number of electrons are involved in the interconversion of the two polymer redox forms, and solvent and salt are allowed to partition into the reduced and the oxidized forms of the polymer. We derive expressions for the concomitant mass changes, taking into account counter-ion, solvent and co-ion (salt) transfer. The results are given in terms of the partition coefficients of solvent and salt between the bathing solution and polymer in its reduced and oxidized states, and a quantity ΔR that describes the difference between co-ion exclusion properties of the polymer in its two different oxidation states. We discuss and illustrate the behaviour of ΔR as a function of electrolyte concentration for systems with different charge type.