REDOX ACTIVITY OF VINYLFERROCENE COPOLYMERS BY ELECTRON HOPPING REACTION IN THE ABSENCE OF FLUID SOLVENTS

A series of novel copolymers consisting of a redox monomer, vinylferrocene, and an ion-conducting monomer, omega-methacryloyl-alpha-methoxy-oligo(ethylene oxide) (average molecular weight = 470), have been prepared by radical copolymerization and characterized. Ionic conductivity and redox activity of the copolymers, complexed with lithium perchlorate, have been explored by using complex impedance spectroscopy and solid state voltammetry with microelectrodes, respectively. The copolymer/salt complexes exhibit ionic conductivity of 10(-5) S cm(-1) at room temperature and chemically reversible redox activity by themselves without any fluid solvents. The redox activity can be assigned to redox reactions of ferrocene sites in the bulk polymeric phases. The redox reactions are caused by propagation of oxidized (reduced) sites, generated at the electrode/copolymer interface, by electron transfer (electron hopping) reactions between mixed valent ferrocene/ferrocenium sites in the diffusion layer. Apparent electron diffusion coefficient for the electron transfer reactions, evaluated by potential step chronoamperometry, increases with increasing vinylferrocene composition in the copolymers. These copolymer/salt complexes are intrinsic redox conductors which exhibit appreciable ionic conductivity and redox activity by themselves without any fluid solvents and can be distinguished from conventional redox polymers.