Electro-oxidation of some soluble alkyl and aryl substituted polysilane homopolymers

Abstract

The electro-oxidation reactions of substituted polysilane homopolymers dissolved in methylene chloride electrolyte were studied using cyclic voltammetry and chronocoulometry. The oxidation waves appear at potentials close to those for the corresponding waves for polymer films, but the current peak height responds linearly to sweep rate, which is unexpected for a diffusion-controlled process. This result suggests some accumulation of the polymer at the electrode surface. In contrast, the diffusion coefficients obtained from chronocoulometry are lower than those for a small molecule, e.g., ferrocene, but appropriate for an electroactive polymer. The oxidation potential is affected by the nature of the substituents on the silicon atom and the effect is reasonable in terms of the electronic characteristics of the substituents. The electrochemical stoichiometry for poly(methylphenylsilane) varies from 0.09 to 0.7 electrons/monomer repeat unit in the chain as the applied potential is changed to more anodic values. The electrochemical stoichiometry for the initial oxidation step of poly(methylphenylsilane) has the value 0.09 electrons/monomer repeat unit in the chain, which agrees with the stoichiometry previously obtained for the polymer as a film on the electrode, 0.1 electrons/monomer repeat unit. A higher stoichiometry was obtained when applying a more anodic potential possibly reflecting the subsequent oxidation of electroactive reaction intermediates. © 1991, The Electrochemical Society, Inc. All rights reserved.