In Situ Optical and Magnetic Measurements of Conducting Poly(trans-1,2-di(2-thienyl)ethylene) Prepared by the Electrochemical Polymerization of cis-1,2-di(2-thienyl)ethylene

Abstract

Preparation of high quality conducting poly(cis-1,2-di(2-thienyl)ethylene), cis-PTE from the electrochemical polymerization of cis-1,2-di(2-thienyl)ethylene was tried. However, synthesized polymer was not cis-PTE but trans-PTE. The electrochemical, optical, and magnetic properties in the trans-PTE in comparison with those of polythiophene, PT, during electrochemical p-type doping have been investigated. These results are discussed in terms of polaron and/or bipolaron models. The band gap of trans-PTE was evaluated to be about 2.1 eV and almost the same as that of PT. The polaron states in trans-PTE appear in the band gap: ca. 0.5 eV above the valence band but ca. 0.8 eV below the conduction band. This result satisfactorily explains the stability of p-type doped trans-PTE compared with that of PT. Since the energy level of the bottom of conduction band in trans-PTE is higher than that in PT by ca. 0.2 eV, and successful n-type doping in trans-PTE is not expected.