Synthesis and characterization of donor-acceptor type quinoxaline-based polymers and the corresponding electrochromic devices with satisfactory open circuit memory

Three novel conjugated polymers were successfully designed and synthesized via the Suzuki coupling reaction based on the donor-acceptor (D-A) strategy. In the synthetic process, a electron rich unit 6,8-dibromo-3,3-bis ((octyloxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProDOT) was selected as the donor unit, 5,8-bis-(5-bromothiopen-3-yl)-2,3-bis-(4-decyloxyphenyl)-quinoxaline (QX) as the acceptor unit, and benzene (B) was the bridging unit. The three polymers are named PBQT-1, PBQT-2 and PBQT-3 by different feed ratios (B:QX: ProDOT) of 2:1:1, 3:2:1 and 3:1:2, respectively. Next, the polymers films are characterized in detail by a variety of instrumental methods. And, the electrochromic devices (ECDs) is also built by employing PBQT-1 and Poly (3,4-ethylenedioxythiophene)(PEDOT) as the anodically coloring material and cathodically coloring material, respectively, which also exhibits the satisfactory open circuit memory. All three polymers display the abundant and obvious color changes, including orange-khaki-dimgray (PBQT-1), brown-tawny-light army green (PBQT-2) and tangerine-brown yellow-light gray (PBQT-3). Meanwhile, the three polymers exhibit medium band gaps and excellent thermal stability, and the initial oxidation potential and optical band gap of the polymers are decreased gradually with the increasing of donor unit. It indicates that the different donor-acceptor ratios can effectively modify the band gap values and colors of the polymers, and provide the prospect to obtain the desired properties. The above results demonstrate that three polymers are anticipated to be the promising candidate for the neutral orange-color electrochromic (EC) materials, deserving more attentions and researches.