Electrochemical preparation and electrochromic properties of random copolymer based on thiophene anthracene unit

The intercalation of anthracene units into polythiophene backbone can significantly regulate the discoloration properties of polymers, but the high polymerization potential leads to poor film-forming quality and properties of polymers. In order to reduce the oxidation potential of monomers containing anthracene units, a monomer 9, 10-bis (2-thiophenyl) anthracene (Th-An-Th) was synthesized by Stille coupling reaction and electrochemically polymerized in polymerization solvent BFEE, BFEE + CF3COOH, LiClO4/ACN and LiClO4/PC, respectively. The results show that th an th is difficult to copolymerize by electrochemical reaction. However, it can be a good comonomer to obtain copolymers with other monomers such as thiophene (Th), 3-methylthiophene (MeTh), 3, 4-ethylenethiophene (EDOT) and selenophone (SePh) via electrochemical copolymerization. The copolymerized films are named as P1, P2, P3 and P4. Cyclic voltammetry and FTIR tests confirm the polymerization process and the characteristic structure of the copolymers. The spectroelectrochemical test results show that the series of copolymers have rich color conversion properties. P1, P3 and P4 films can change four colors under -0.6 V to 1.0 V scanning, and show good near-infrared discoloration ability. The copolymer film has fast switching response rate and good electrochemical stability. The bleaching and coloring response times of P4 film at 521 nm are 1.9 s and 3.4 s, respectively, and the optical contrast is 35.6%. After 210 switching cycles, the optical contrast of the copolymer is only lost by 2.3%, and the electrochemical activity of the copolymer remains 82% after 400 cycles.