Preparation and Photochromic Properties of Nanocapsules Containing Azo Compound with Polyurethane as Wall Material Using in Situ Polymerization

Photosensitive color-producing nanocapsules have been prepared with polyurethane as wall material via an in situ polymerization method. The polyurethane shell slowed down the colorization process for 12 s compared with azo compound in ethanol; however, the absorbance of azo compound increased by 29.7% in polyurethane nanocapsules. The absorbance of photoisomer decreased by 50% of the photostationary value during 60 s in polyurethane nanocapsules and 14 s in ethanol. The color depth of polyurethane nanocapsules was higher at the end of decolorization process. The half-life of azo compound and polyurethane nanocapsules were 135 min and 280 min, respectively.