Synthesis and characterization of poly(thiophene sulfides)prepared via chemically initiated oxidative polymerization methods

Poly(3,4-ethylenedioxythiophene)(Poly(1)), poly(bis(3,4-ethylenedioxy-2-thienyl)sulfide)(Poly(2)) and poly(bis(2-thienyl)sulfide)(Poly(3)) have been prepared via chemical polymerization using either FeCl3 or NOBF4 as oxidizing agents. The stability of the thiophene-sulfur bonds in the presence of FeCl3 has been discussed for Poly(2)and Poly(3). These polymers are stable and have been characterized by UV-vis spectroscopy. Poly(1)and Poly(2)exhibit multiple peaks between 400 and 600 nm independent of the oxidizing agent used. Poly(3)has an absorption maxima at 398 nm. In the doped state, Poly(1)-NOBF4, Poly(2)-NOBF4 and Poly(3)-FeCl3 are not conducting, whereas Poly(1)-FeCl3 and Poly(2)- FeCl3 display an electrical conductivity of 12.5×10-4 and 2×10-4 S/cm, respectively. A copolymer resulting from the polymerization of a mixture of 3,4-ethylenedioxythiophene (1)and bis(3,4-ethylenedioxy-2-thienyl)sulfide (2)(1:1)displays an electrical conductivity close to that of Poly(1)-FeCl3.