UV-Vis irradiation fatigue resistance improvement of azo photochromic compound using polyurethane-chitosan double shell encapsulation.

ABSTRACT Double shell photochromic microcapsules were prepared by in situ polymerization with polyurethane and chitosan as inner and outer shell respectively. FT-IR indicated that chitosan-glutaraldehyde copolymer formed by imine and combined with polyurethane photochromic nanocapsules. The polyurethane-chitosan microcapsules exhibited a near-spherical shape, and the average particle size of nanocapsules was around 1.2 μm. The half-life of azo compound increased from 135 to 340 min after encapsulated in polyurethane-chitosan microcapsules. The polyurethane-chitosan shell delayed the coloration process for 14 s compared with azo compound in ethanol, however, the absorbance of azo compound increased by 17.15% in polyurethane-chitosan microcapsules. It decreased from 0.3486 to 0.1738 in ethanol during 20 s, however, it decreased from 0.4084 to 0.2625 in polyurethane-chitosan microcapsules in 55 s when it reached steady state during decoloration process. Polyurethane-chitosan double shell encapsulation is an effective route for improving the fatigue resistance, increasing the absorbance of azo compound. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40895. [ABSTRACT FROM AUTHOR]