Abstract Three novel donor-accept type electrochromic polymers with very low band gap, namely PMFTTP, PMFBTTP and PMFMOTTP, were prepared via electrochemical polymerization, employing 2,3-bis(5-methylfuran-2-yl)thieno[3,4-b]pyrazine as the acceptor units and thiophene, butylthiophen and methoxythiophen as the donor units, respectively. All the polymers were comparatively studied by cyclic voltammetry (CV), scanning electron micrographs (SEM), UV–vis-NIR spectroscopy and colorimetry. The results revealed that PMFTTP and PMFBTTP showed obvious color change from green color to brown in the oxidation process, while PMFMOTTP exhibited color change from brick red to dark gray. And the three polymers possessed very low optical band gaps in the following order: PMFTTP (1.23 eV) > PMFBTTP (0.88 eV) > PMFMOTTP (0.74 eV), which demonstrated the different election-donating ability of thiophene or its derivatives. The electrochromic kinetic investigations manifested that the polymers presented satisfactory optical contrasts (ΔT%) in the near infrared region (NIR), which were 35%, 67% and 60% for PMFTTP, PMFBTTP and PMFMOTTP, respectively. Moreover, the polymers also displayed short switching times (lower than 1 s at any wavelengths), high coloration efficiencies (around about 200 cm2/C) and outstanding robust stabilities, suggesting the probability of being the promising candidates for the electrochromic devices. In summary, the above positive results, especially the neutral green color and the very low band gap, had important theoretical significance for the application and development of electrochromic polymers.

中文翻译：

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含有 2,3-双(5-甲基呋喃-2-基)噻吩并[3,4-b]吡嗪受体和不同噻吩供体的三种新型供体-受体型电致变色聚合物：低带隙、中性绿色、快速-切换材料

摘要 采用 2,3-双(5-甲基呋喃-2-基)噻吩并[3,4-b]电化学聚合方法制备了三种新型的极低带隙供体-受体型电致变色聚合物，即PMFTTP、PMFBTTP和PMFMOTTP。 ]吡嗪作为受体单元，噻吩、丁基噻吩和甲氧基噻吩分别作为供体单元。通过循环伏安法 (CV)、扫描电子显微照片 (SEM)、UV-vis-NIR 光谱和比色法对所有聚合物进行了比较研究。结果表明，PMFTTP和PMFBTTP在氧化过程中呈现明显的颜色由绿色变为棕色，而PMFMOTTP则呈现出由砖红色变为深灰色的颜色。并且这三种聚合物按以下顺序具有非常低的光学带隙：PMFTTP (1.23 eV) > PMFBTTP (0.88 eV) > PMFMOTTP (0.74 eV)，这证明了噻吩或其衍生物具有不同的选举供体能力。电致变色动力学研究表明，聚合物在近红外区域 (NIR) 表现出令人满意的光学对比度 (ΔT%)，PMFTTP、PMFBTTP 和 PMFMOTTP 分别为 35%、67% 和 60%。此外，该聚合物还显示出短切换时间（在任何波长下都低于 1 秒）、高着色效率（约 200 cm2/C）和出色的稳健稳定性，表明有可能成为电致变色器件的有希望的候选者。综上所述，上述积极成果，尤其是中性绿色和极低的带隙，对电致变色聚合物的应用和发展具有重要的理论意义。