Two-dimensional tungstate nanosheets for constructing novel photochromic hydrogel with ultrahigh flexibility

A hydrogel possessing interesting photochromic behaviors was developed by in situ ultraviolet(UV)irradiation-assisted polymerization of an aqueous solution of N-isopropylacrylamide monomer in the presence of cesium tungstate nanosheets.By this process,a hierarchical porous network structure was finely constructed while showing ultrahigh flexibility.More importantly,the newly prepared hydrogel retained the photochromic properties of the cesium tungstate nanosheets.The color transitions could be readily controlled by UV laser irradiation and were completely reversible via laser exposure or dark treatment.The nanocomposite hydrogel with its excellent photochromic properties and ultrahigh flexibility will have great applications in flexible photochromic devices.The synthetic procedure is simple and has promises to be extended to developing other hydrogels with various new functionalities.