The Preparation and Electrochromic Properties of the Polyurethanes Containing Triphenylamine Moiety

Electrochromism is a phenomenon that optical changes of chemical materials occur in a reversible electrochemical process. For electrochromic polymers, the electrochromism is related to the changing of band gaps during the doping-dedoping process. The color changes are commonly between a transparent state, where the chromophore only absorbs in UV region and colored state, or between two colored states in a given electrolyte solution.

Two series of novel triphenylamine-containing aromatic polyurethanes (PUs) were synthesized via polycondensation of N, N-bis (4 - diisocyanate) -4 -N'- carbazolyl-1,4-aniline, and N, N-bis (4 - diisocyanate) -4 -N'- carbazolyl-1,4-phenylenediamine with various dihydroxy such as phenolphthalein, bisphenol A, 4,4'-dihydroxybiphenyl, 4,4'-bishydroxybenzophenone, bisphenolfluorene. The variation of the backbone structure significantly affected the dihedral angles and changed the electronic properties, solubility, molecular weight and thermal stability of PUs. The obtained PUs exhibited stable and reversible electrochromic properties. The color of PUs can be varied from initial colorless to green, then to blue via electro-oxidation. Considering the sensitive chromic properties of PUs, they will have potential applications for eletrochomic materials.

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