Mediated electron transfer reactions at electrodes coated with poly(viologen)s

Abstract

Electron and ion transport processes in microdomains of pendant-type poly(viologen)s were analysed by means of rotating disc voltammetry in aqueous media. Stability of poly(viologen)s on the electrode was improved by introducing long alkyl chains. Penetration or the diffusion of ions and the electron-propagation through the polymer layers were greatly affected by the type of supporting electrolyte and chain length of side alkyl groups. Indeed, almost no penetration of large anionic ions was observed in the case of pendant-type poly(viologen) possessing cetyl groups in a perchlorate supporting electrolyte. The electron-propagation through the polymer layers by the self-exchange reactions among redox-active viologen units seemed also to be slow, as the migration of the counter anion of poly(viologen) was limited inside the cationic domain. Similar behaviour was observed in the case of poly(viologen) coatings with ethyl pendant groups, but the electron-propagation was much slower in comparison with the former case. This difference could be attributed to the nature of cationic domains, since the polycations with long alkyl side chains might form a polymer micelle structure with a segregated hydrophobic domain and cationic channel for the electron-propagation.