Electron transfer reaction between fixed redox sites in ion/electron mixed conducting polymers

Summary form only given. Electrochemical reaction of redox molecules introduced in ionically conducting polymers can occur by two mechanisms. One mechanism is the physical diffusion of redox molecules to eletrode, followed by electron transfer reaction, and the other is the propagation of oxidized (reduced) sites generated at the electrode by electron self exchange reaction between redox sites. Redox active ion-conducting polymers whose reaction occurs by the latter mechanism are called ion/electron mixed conductors or redox conductors. In this study, the electron transfer mechanism at redox reaction has been examined in ionically conducting polymers having fixed redox sites. The polymers were prepared by radical copolymerization of vinylferrocene(VFc) or 3-vinyl-N-methylphenothiazine(VPT) as a redox monomer with methoxy nona(ethylen oxide) metacrylate(ME0/sub 9/) as an ionically conducting monomer. Reversible redox reaction in the bulk polymeric phase was observed in these copolymers, although the redox sites are affixed to the polymer backbone. Apparent diffusion coefficient (D) of the redox sites in the VFc-MEO/sub 9/ copolymers linearly increaced with increasing VFc composition with an intercept close to zero, which shows that D in the copolymer corresponds to the electron diffusuvity. Temperature dependence of the electron diffusion coefficient was very large and fit WLFeq. This indicates that the electron exchange rate greatly changes with temperature and is influenced by the dynamics of the polymer backbone. The electron transfer behavior in the VPT-ME0/sub 9/ copolymers were also explored and compared in these two series of the copolymers.