Kinetics of redox switching of electroactive polymers usig the electrochemical quartz crystal microbalance Part I. Identifying the rate limiting stip in the presence of coupled electron/ion and solvent transfer

摘要

The oxidation of poly(vinylferrocene)(PVF)films in aqueous athing solutions proceeds via the oxidation of the uncharged PVF followed by entry of water into the film. The hcange in mechanism betwee nrate controlling coupled electron/ion and solvent transfer was studied in 0.1M sodium perchlorate athing solution using the electrochemical quartz crytal microbalance(EQCM). The film's redox switchin was investigated using cyclic voltammetry at voltage scan rates between 0.004 and 0.080 Vs~(-1), The controlling kinetic step depends on the instantaneous oxidation state of the film, the voltage scan rate and its direction. These quantities deterine the relative fluxes of water and counter ion during the redox cycle; the flux ratio at any charge level is diagnostic of the instantaneous rate determining step. We give these diamostic relations, and show how to the EQCM data to obtain these flux ratios. The flux ratio that maintains the(pseudo)equilibrium population ratio in th PVF film is the dividing line between kinetic control by water transfer or counter ion transfer. High charge fluxes are likely to be associated with kinetic control by solvent transfer. Low charge fluxes lead to kinetic control by coupled electron/counter ion transfers. Both kinetic situations are observed with PVF under the codition that were used here