A neutron reflectivity study of [Os(bipy)(2)(PVP)(10)Cl](+) polymer film modified electrodes: effect of redox state and counter ion

The effects of redox state (Os[II] vs. Os[III]) and counter ion (perchlorat e vs, p-toluenesulphonate) on the polymer and solvent density distributions in films of electroactive [Os(bipy)(2)(PVP)(10)Cl](+) were determined usin g neutron reflectivity. The changes in polymer structure upon immersion in solvent and upon redox cycling the film in these electrolytes were also inv estigated. The as-prepared dry polymer film swelled appreciably upon immers ion in aqueous solutions. Using p-toluenesulphonate as the counter ion caus ed pronounced changes to film structure upon both redox cycling and holding it in a fixed oxidation state; the perchlorate anion was found to be much less disruptive. Surprisingly, the effect on film structure of changing ani on was much more pronounced than the effect of changing film redox state, i .e. charge density. (C) 1999 Elsevier Science Ltd. All rights reserved.