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.