The preparation and electrochromic properties of the polyurethanes containing triphenylamine moiety

A novel series of triphenylamine-containing aromatic polyurethanes (PUs) were synthesized via polymerization of N,N-bis (4-isocyanatophenyl) aniline monomer with different dihydroxy compounds. The structures of PUs were characterized by means of Fourier transform infrared (FTIR), 1H nuclear magnetic resonance (1H NMR) spectroscopy which showing an agreement with the proposed structure. All the PUs are soluble in a variety of organic solvents, and could be cast into transparent, tough films with good mechanical properties. The effects of molecular structure on thermal stability of the polymers were studied by thermo-gravimetric analyzer. The electrochemical behaviors were investigated by cycle voltammetry (CV) method, and the result revealed that there were a pair of reversible oxidative redox couples at potentials of 0.33 V and 1.15 V vs Ag/AgCl in acetonitrile solution. The electrochromic properties were examined by spectroelectrochemical methods. All the PUs exhibited excellent reversibility of electrochromic characteristics by continuous cyclic scans between 0 V and 1.6 V, with a color changing from yellow to blue.