Synthesis and electrochemical properties of mixed ionic and electronic modified polycarbazole

A carbazole N-substituted by an oxyethylene group was polymerized using oxidative electro-polymerization. Due to the hydrophilic properties of the oligooxyethylene substituent, this monomer can be solubilized and electropolymerized in aqueous electrolyte solution. An acidic medium is particularly appropriate in order to decrease the oxidative potential and to obtain films mainly composed of short oligomers as revealed by GPC analysis. By comparison, the chemical polymerization of the corresponding 3,6 dibromo derivative leads to oligomers with well-defined structure and leads to the obtention of longer macromolecular chains. Electrochromic properties of these materials have been studied and a transition from colorless to deep green has been observed during the oxidation. More particularly interesting are the stability of such materials during polarization and the kinetics of diffusion of the counter ion in the film. In acidic medium 1.25 mol l −1 HClO 4, 95% of the charge density was maintained after polarization for 7000 cycles which shows the good electrochemical stability of this material compared with other polycarbazoles. Diffusion coefficient have been evaluated in aqueous media about D ClO 4 − =10 −11 cm 2 s −1. Moreover, films are electroactive in oxyethylene based electrolytes. Then, they are probably well-compatible with hydrophilic poly(oxyethylene) solid electrolytes such that all-polymer devices may be prepared.