A novel multichromic copolymer via electrochemical copolymerization of (S)-1,1′-binaphthyl-2,2′-diyl bis(N-(6-hexanoic acid-1-yl) pyrrole) and 3,4-ethylenedioxythiophene

Copolymer based on (S)-1,1′-binaphthyl-2,2′-diyl bis(N-(6-hexanoic acid-1-yl) pyrrole) (BPL) and 3,4-ethylenedioxythiophene (EDOT) is electrochemically synthesized and characterized. The comonomers exhibit relatively closer onset oxidation potentials, implying that the electrochemical copolymerization is relatively easy to be achieved. Electrochemical methods, FTIR, ¹H NMR and UV-vis analysis confirm that the resulting polymer is a copolymer rather than a blend or a composite of the respective homopolymers. Spectroelectrochemical analysis reveals that the copolymer film has distinct electrochromic properties from that of the BPL homopolymer film and shows six different colors under various potentials. At the neutral state of the copolymer, the π → π* transition absorption peak is located at 535 nm and E_g is calculated as 1.78 eV. The copolymer film shows a maximum optical contrast (ΔT%) of 31% and a switching time of 1.2 s which are higher and faster than those of the homopolymer of BPL (PBPL, 7.8% and 2 s). The new multichromic copolymer is thermally stable up to 345 °C and is electrochemically stable up to 1.39 V. SEM images illustrate that the copolymer film presents a much smoother surface than that of the respective homopolymers.