3,4-Ethylenedioxy-substituted bithiophene-alt-thiophene-S,S-dioxide regular copolymers. Synthesis and conductive, magnetic and luminescence properties.

Abstract

Polyconjugated regular bithiophene-alt-thiophene-S,S-dioxide copolymers were produced by anodic coupling of variously 3,4-ethylenedioxy-substituted 2,5-bis(2-thienyl)thiophene-S,S-dioxide. The polymers were characterized by cyclic voltammetry, FTIR reflection-absorption and UV-vis spectroscopy, MALDI-TOF mass spectroscopy, electrochemical quartz crystal microbalance, in situ ESR and in situ conductivity techniques, photo- and electro-luminescence measurements. The regular alternation of electron-rich and -poor thiophene rings in the polymer chain operated by the ethylenedioxy and S,S-dioxide moieties produces a finite window of conductivity. Alkyl-protection of the β-positions of the thiophene-S,S-dioxide ring gave low-defect and soluble oligomers which were investigated in single-layer organic light-emitting devices (OLEDs). Photoluminescence quantum efficiency of ca. 1% and external electroluminescence quantum efficiencies of 0.01% photon/electron at a luminance of 100 cd m⁻² were obtained.