Responses of Poly(vinylferrocene) Film Redox-Driven Exchange Process to Codeposited and Ambient Anions

Abstract

We describe redox switching of polyvinylferrocene (PVF) films deposited from CH2Cl2 and sequentially exposed to aqueous solutions of three different charge neutralizing anions (BF4-, ClO4-, PF6-). EQCM charge and mass responses to PVF redox cycling in these aqueous media are combined to provide the potential dependence of ion and solvent fluxes for different experimental time scales. We find that the size of the anion initially introduced into a PVF film when it is deposited from CH2Cl2 determines the free volume that exists when the film is subsequently immersed in aqueous solution. We develop a model based upon free volume in which anions and solvent compete for space within the film. The model successfully predicts the result that the larger the anion the less solvent transfers, the effect of initially co-deposited anion on subsequently available free volume, and the decrease in mobile species transfers with decreasing time scale.