Highly Conducting Water-Soluble Polythiophene Derivatives

Water-soluble sodium poly(2-(3-thienyloxy)ethanesulfonate) and sodium poly(2-(4-methyl-3-thienyloxy)ethanesulfonate) have been synthesized. The sulfonic acid form of these new polymers has revealed a self-acid-doping reaction that leads to stable, highly conducting (0.5−5 S/cm) materials together with low absorption in the visible range. This process is reversible, and upon deprotonation, the insulating and dark polymers are recovered. The high doping and conductivity levels seem to be related to the relatively low oxidation potentials (0.44−0.50 V vs Ag/AgCl) of these polymers, which allows an almost complete (reversible) oxidation reaction in air (oxygen), catalyzed by the presence of the sulfonic acid moiety.