ELECTROCHEMICAL MEASUREMENTS OF DIFFUSION-COEFFICIENTS OF REDOX-LABELED POLY(ETHYLENE GLYCOL) DISSOLVED IN POLY(ETHYLENE GLYCOL) MELTS

Ferrocene-labeled monomethoxy-poly(ethylene glycol)s (MPEG) with molec ular weights of 1900 and 750 were used as redox probe solutes in poly( ethylene glycol) melt solvents of molecular weight 750, 2000, and 20 0 00. Cyclic voltammetry and chronoamperometry at microdisk electrodes w ere employed to measure the diffusion coefficients of the redox probes , which were independent of the probe concentration and varied between 10(-7) and 10(-10) cm(2)/s. Diffusional activation barrier results al so suggest that the ferrocene label does not significantly influence t he diffusivity of the probe molecule in the host solvent. Activation b arrier, viscosity, and ionic conductivity results show that the LiClO4 electrolyte does not influence the diffusion. barrier or viscosity as long as the ether O/Li+ ratio is greater than or equal to 250 (ca. 0. 1 M) which is still a sufficient electrolyte concentration to allow qu antitative electrochemical diffusion measurements.