Optical study on electrochemical and chemical doping of polymers of oligothienyls bridged by monosilyl

Electrochemical doping and in-situ UV-vis-NIR spectroelectrochemical proper ties of solid films of some sigma-pi conjugated polymers consisting of alte rnating oligothienylene units and silylene units have been investigated in acetonitrile, while chemical doping of these polymers has been conducted in dichloroethane. The cyclic voltammograms of the films of these polymers sh ow two couples of redox peaks in the potential range of 0-1.2 V. The doping -level measurements and the in-situ spectroelectrochemical measurements sug gest that the repeat unit of the polymer chain is oxidized to the radical c ation in the first-step oxidation, and to the dication in the second-step o xidation. In addition, the in-situ UV-vis-NIR measurements provide clear-cu t evidence for the transitions from the radical cation to their pi-dimers v ia a coupling reaction. The changes in the absorption spectra of the polyme r films at different potentials are interpreted by considering the dimeriza tion reaction of the radical cations to the pi-dimers. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.