Electrochemical properties of oligothienylene–oligosilanylene block copolymers: Influences of block sizes

Abstract

The fundamental electrochemical properties of oligothienylene–oligosilanylene block copolymers, especially the influences of the block sizes, were studied in acetonitrile. In electrochemical oxidation, films of the polymers containing Si–Si bonds suffer more or less from decomposition and dissolution due to partial cleavage of the Si–Si bonds in the oligosilanylene units. Decomposition decreases as the oligosilanylene block size decreases, and is not observed with copolymers containing no Si–Si bond, that is, oligothienylene–monosilanylene copolymers. The copolymer films can also be electrochemically anion doped. Cyclic voltammograms obtained at high scan rates generally exhibit a two-step oxidative doping process, though the second-step oxidation is hardly seen for polymers with smaller oligothienylene blocks. The potentials of the oxidative doping peaks show a cathodic shift as the oligosilanylene block size increases because of the σ–π-interaction in the polymer chains and the action of the oligosilanylene block as a spacer, both of which are favourable to the stabilization of the cations and dications generated in the polymer chain.