Polyurethanes prepared from isocyanates containing triphenylamine derivatives: synthesis and optical, electrochemical, electrochromic and memory properties

Two novel series of triphenylamine (TPA)-containing aromatic polyurethanes (PUs) were synthesized via polymerization of N', N'-bis(alpha-naphthyl)-N, N'-bis(4-phenylisocyanate) biphenyl (M1) and N, N'-diphenyl-N, N'-bis(4-phenylisocyanate) biphenyl (M2) with different dihydroxy compounds. The structures of the polymers were characterized by Fourier transform infrared (FT-IR) spectroscopy, hydrogen nuclear magnetic resonance (H-1-NMR) and carbon nuclear magnetic resonance (C-13-NMR); and the thermostability and morphology were studied by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The molecular weights were measured to be from 1.02 x 10(4) to 1.31 x 10(4) by gel permeation chromatography (GPC). The polymers were coated onto indium tin oxide (ITO) and the electrochromic properties were investigated by using the ultraviolet visible (UV-vis) absorption spectra and cyclic voltammetry (CV). The energy gaps were in the range of 2.21-2.26 eV. The polymer films revealed good stability of the electrochromic characteristics by continuous cyclic scans, with the color changing from neutral yellowish to a blue doped form at applied potentials. Meanwhile, the PUs film exhibited non-volatile write-once-read-many-times (WORM) memory behavior in the device resulting from the non-isolated donor-acceptor (D-A).