Preparation and electrochromic properties of two series of polyurethanes containing separated triphenylamine moiety with different blocks

Two series of novel aromatic polyurethanes containing triphenylamine derivatives were synthesized via polycondensation of 4-(3,6-diisocyanato-9H-carbazol-9-yl) aniline, N,N-bis(4-isocyanatophenyl) benzene-1,4-diamine with various dihydroxy monomers such as phenolphthalein, 2,2-bis (4-hydroxyphenyl) -propane, 4,4'-dihydroxybiphenyl, 4, 4'-bishydroxy benzophenone and bisphenolfluorene, respectively. The variation of the backbone structure affected the electronic properties, solubility, molecular weight and thermal stability of polyurethanes. The thermal stability of polyurethanes was studied by the gravimetric analyzer. The electrochromic performance was investigated by cyclic voltammograms and spectroelectrochemical methods, which showed stable and reversible electrochromic properties. Besides, the color of polyurethanes can be varied from initial colorless to green then to blue via electro-oxidation, which indicates the polyurethanes will have potential applications for eletrochromic materials. In addition, the PUs exhibited memory characteristic. The result indicated the PUs could be applied in smart window and memory devices.