Synthesis, electrochemistry, and electrochromic properties of branched thiophene polymers with different conjugation lengths

Here the authors designed and synthesized three branched thiophene polymers with different effective conjugation lengths of thiophene groups, pTPBT, pTPTT, and pTPQT, mainly based on bithiophene, trithiophene, and quadruple thiophene. The electrochemical curves and theoretical calculation results reflect that the oxidation potential of polymers decreased gradually as the conjugation lengths of thiophene groups increased, which is favorable for the appearance of electrochromism. Electrochromic properties demonstrate that pTBTT displays no electrochromism, pTPTT exhibits an unstable one, while pTPQT shows an obvious stable electrochromism between yellow‐orange and blue‐violet colors. These results indicate that thiophene polymers with effective electrochromism should be the smallest conjugation length of quadruple thiophene at least. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2340–2348