Preparation and photochromic properties of waterborne polyurethane containing spirooxazine groups

Two novel photochromic spirooxazines, SO 1 and SO 3, were successfully prepared and characterized by Fourier transform infrared spectroscopy (FTIR), ¹H-NMR, and mass spectrometry with electrospray ionization (ESI-MS). SO 1 was doped and grafted with waterborne polyurethane (WPU) to afford D₁-WPU and G₁-WPU. D₃-WPU was prepared by doping SO 3 with waterborne polyurethane. FTIR spectra indicated that SO 1 was grafted onto waterborne polyurethane successfully. Scanning electron microscopy proved that spirooxazines of D-WPU can be effectively dispersed in a waterborne polyurethane matrix, and spirooxazines of G-WPU are evenly distributed in the copolymer. The results showed that the light transmittance of modified waterborne polyurethane films decreased compared with pure waterborne polyurethane films, but the water resistance and tensile strength were better. Ultraviolet–visible spectra demonstrated that the thermal stability of spirooxazine derivatives improved significantly after being modified. The fading rate constant of the D₃-WPU film (k = 0.0079 s^-1) during the discoloration process decreased 9.77 times in contrast to SO 3 in ethanol, which showed that the thermal stability of spirooxazine in WPU film was obviously enhanced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47067.