Absorption properties of alkoxy-substituted thienylene-vinylene oligomers as a function of the doping level

In an attempt to improve on the properties of PEDOT (poly(3,4-ethylenedioxythiophene)) as a stable, conducting, and transparent coating we synthesized four different alkoxy-substituted poly(thienylene-vinylene)s, 1-4, using the Stille coupling reaction. The oligomers and polymers obtained were characterized and their NIR-vis absorption spectra were measured as a function of doping, both electrochemically as films and chemically in solution. Similar spectra of PEDOT films were gathered for comparison. In PEDOT a change in doping level does not change the energies of the absorption bands, while for the other polymers the bands shift markedly and the NIR peak at high doping level lies at a higher energy. The polymers 1-4 are much less suited for the intended coatings than PEDOT. Possible reasons for this are discussed.