A STUDY OF FERROCENE DIFFUSION DYNAMICS IN NETWORK POLY(ETHYLENE OXIDE) POLYMER ELECTROLYTE BY SOLID-STATE VOLTAMMETRY

The diffusion rates of five ferrocene derivatives dissolved in an amorphous, cross-linked poly(ethylene oxide) (PEO) polymer electrolyte are measured by an electrochemical technique which detects the rate of their transport to an oxidizing microdisk electrode. The diffusion coefficients in dilute ferrocene/polymer solutions at 65°C vary from 3 × 10-7 to 2 × 10-8 cm2 s-1 depending on the size of the ferrocene derivative. The diffusion coefficients decrease with increasing ferrocene concentration, increasing LiClO4 electrolyte concentration, and decreasing temperature; values approaching 10-10 cm2 s-1 are encountered at room temperature. The concentration dependencies conform to a simple free volume model. The qualitative similarities of the temperature and concentration dependencies of the ferrocene diffusion rates to the behavior of ionic conductivity of network PEO/LiClO4 solutions suggest that the decrease in ionic conductivity observed at high electrolyte concentration is due to a decrease in the ionic diffusivity. © 1990 American Chemical Society.