Copolymers of 3,4-Ethylenedioxythiophene and of Pyridine Alternated with Fluorene or Phenylene Units: Synthesis, Optical Properties, and Devices

Abstract

We report the synthesis of four conjugated copolymers based on alkylated fluorene or phenylene units which band gap is tuned by the regular insertion of an electron-donating or electron-withdrawing unit, (3,4-ethylenedioxy)thiophene and pyridine, respectively. The (AB)n regular sequence is achieved by Suzuki polycondensation reactions. The characterization of the copolymers by size exclusion chromatography reveals chains lengths of about 20−30 repeat units (40−60 rings), leading to a good processability for potential optical applications. The 1:1 ratio between the two units improves the solubility of the material in common organic solvents, allowing for physicochemical characterizations. Raman and FT-IR experiments indicate that the electronic structure of the backbone is rather benzenic in the neutral (undoped) state, as opposed to a quinoic oxidized structure. All copolymers exhibit interesting electrochromic properties as attested by cyclic voltammetry and UV−vis experiments. They reversibly switch amo...