A novel multichromic copolymer of 1,4-bis(3-hexylthiophen-2-yl)benzene and 3,4-ethylenedioxythiophene prepared via electrocopolymerization

Copolymer based on 1,4-bis(3-hexylthiophen-2-yl)benzene (BHThBe) and 3,4-ethylenedioxythiophene (EDOT) is electrochemically synthesized and characterized. Electrochemical methods, FTIR and 1H NMR analyses confirm that the resulting polymer is a copolymer rather than a blend or a composite of the respective homopolymers. Moreover, the spectroelectrochemical and electrochromic properties of the copolymer films are investigated. According to the spectroelectrochemical analyses, the copolymer film reveals distinct electrochromic properties from that of the BHThBe homopolymer film and shows five different colors under various potentials. At the neutral state of the copolymer, the π → π* transition absorption peak is located at 401 nm with a shoulder around 510 nm and the energy gap is calculated as 1.86 eV. The copolymer film shows a maximum optical contrast (ΔT%) of 36% in visible region with a switching time of 1.8 s and of 76% in the near-IR region with a switching time of 1.4 s. The new multichromic copolymer is thermally stable up to 315 °C and is soluble in chloroform. SEM images illustrate that the copolymer film presents a much smoother surface than that of the respective homopolymers.