Electrochemical polymerization of a new low-voltage oxidized thienylenepyrrole derivative and its electrochromic device application

• A new monomer based on terthienyl system was synthesized and polymerized by electrochemical methods.
• Optical and electrochemical properties were investigated.
• All polymer films have p-type doping and exhibited multichromic properties.

Synthesis of a new monomer, 2,5-bis-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1-phenyl-1H-pyrrole (ENE), from pyrrole, iodobenzene and 3,4-ethylenedioxythiophene (EDOT), and its electropolymerization are reported. ENE was oxidized at a low oxidation potential (0.45 V vs. Ag/AgCl) and successfully electropolymerized in acetonitrile containing 0.1 M NaClO4 and LiClO4 electrolyte mixture. The resulting polymer, P(ENE), revealed five distinctive colors upon doping, which indicated that the polymer is multichromic. P(ENE) has a coloration efficiency of 288 cm2/C at 422 nm with a specific optical band gap of 2.0 eV. Furthermore, an electrochromic device (ECD) based on P(ENE) and poly(ethylene dioxythiophene) (PEDOT) was constructed and its switching was investigated by UV–vis spectroscopy.

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