Multi-color electrochromism containing green color based on electrochemically polymerized star-shaped phenyl bithiophene

Abstract

A star-shaped thiophene derivative, namely PHBT, consisting of one central core of phenyl and three arms of bithiophene, was newly synthesized and characterized, in order to further investigate the relationship between the star-shaped monomer structure (central core and peripheral arm) and the polymeric electrochromic properties. Then it was further successfully prepared into the corresponding cross-linked polymer pPHBT via electrochemical polymerization. After applying positive voltage, pPHBT exhibited excellent electrochromic properties with surprising multi-color changes between three colors, orange-yellow, green and blue, and a fast color switching speed. Furthermore, electronic structure, cyclic voltammetry and electrochromic results of pPHBT can contribute much to explain the electrochromic behavior of pTPABT with the triphenylamine core and the quadruple thiophene arm. The electrochromism of pTPABT might consist of two parts derived from the oxidative states of triphenylamine and quadruple thiophene groups, respectively. This offers a new insight into the electrochromism mechanics of conjugated polymers.

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Recent advances in electrochromic materials and devices for camouflage applications

“…Using this strategy, a lot of green and yellow EC materials for adaptive color camouflage have been designed and synthesized, such as small organic molecules, [79][80][81][82] metal-organic complexes, 83,84 and conjugated polymers. [85][86][87] Small organic molecules mainly include viologen and its derivatives, 88,89 organic redox dyes, 16,90 etc. Among various small molecule EC materials, the cathodic EC material 1,1 0disubstituted-4,4 0 -bipyridinium salts, commonly called viologens, is by far the most intensively investigated.…”

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“…The polymer electrochromic (PEC) materials are one of the research hotspots at present because of their advantages of easy tailoring of their molecular structure, wide range of color change, high‐optical contrast, fast switching time, and excellent processability and so forth 4–8 . At present, the rich color display properties of PEC materials can be realized by molecular structure design or modification, such as donor‐acceptor (D‐A) structure design, introduction of functional groups and copolymerization of different monomers 9–13 . However, fast switching time and long‐term cycle stability, for commercial applications, are also indispensable requirements.…”