Publication 554

Contribution from the Laboratoire d'Electrochimie Moléculaire de l'Université Denis Diderot (Paris 7), UMR CNRS 7591, 2 place Jussieu, 75251 Paris Cedex 05, France

In the first part of the study, PEG₃₄₀₀-Fc linear polymeric chains bearing an electrochemically active ferrocene (Fc) head at their loose end are terminally attached at the gold electrode surface. The surface concentration of grafted polymeric chains is measured electrochemically under good solvent (water) conditions, and in the present work, it appears that the electrode is covered with terminally attached PEG chains in the mushroom configuration. The dynamics of the terminally attached chain can be completely characterized according to a model of elastic bounded diffusion which requires the knowledge of the diffusion coefficient D of the loose end and a spring constant, k_spr, that is entropic in nature. Both D and k_spr are determined. In the second part, the electrode is coated with terminally attached PEG₃₄₀₀ and PEG₂₀₀₀₀ chains which are not electrochemically active. The rate constants of penetration and escape of mobile HO-PEG₃₄₀₀-Fc chains in and out of the polymeric coating were determined together with the partition coefficient of HO-PEG₃₄₀₀-Fc between the coating and the surrounding aqueous solution.