Synthesis and Photochromism Properties of Anionic Waterborne Polyurethane Containing Azobenzene Chromophores

摘要

A series of novel waterborne polyurethane dispersions (HPB-WPU) possessing the property of photochromism was prepared from isophorone diisocyanate (IPDI), polytetramethylene ether glycol (PTMG), and 2, 2-dimethylol propionic acid (DMPA) using a self-made azo diol, N, N-bis-(2-hydroxy-ethyl)-4-phenylazo-aniline (HPB), as a chain extender to partially substitute for 1, 4-butanediol (BDO). The molecular structures of HPB and HPB-WPU were confirmed using Fourier-transform infrared spectroscopy. The photochromism of HPB and HPB-WPU was evaluated using ultraviolet visible (UV-Vis) absorption spectroscopy during the test. The results indicated that when the dispersion was placed under UV irradiation, the color and absorption intensity both changed. The UV-Vis absorption showed a blue shift effect of about 33nm when HPB was blocked into polyurethane chains. The azo chromophore became permanently fixed into the molecule, and the dispersions remained stable for a long time because of the covalent bonding with polyurethane chains during synthesis. There were no precipitates or any other changes after they had been allowed to remain at room temperature for half a year. The synthesized HPB-WPU was also investigated using differential scanning calorimetric analysis, particle size analysis, and water resistance analysis. It was observed that HPB could improve the thermostability, emulsion stability and water-resistant property of the waterborne polyurethane.