Photochromic Inorganic/Organic Thermoplastic Elastomers

Photochromic materials are an important class of smart materials and are broadly utilized in technological devices. However, most photochromic materials reported so far are composed of inorganic compounds that are challenging to process and suffer from poor mechanical performance, severely limiting their applications in various markets. In this paper, inorganic photo-chromic tungsten trioxide (WO3) nanocrystals are conveniently grafted with polymers to hurdle the deficiency in processability and mechanical properties. This new type of photochromic material can be thermally processed into desired geometries like disks and dog-bone specimens. Fully reversible photochromic response under UV light is also achieved for WO3-graft polymers, exhibiting tunable response rate, outperforming the pristine WO3 nanocrystals. Notably, the resulted graft polymers show extra-ordinary mechanical performance with excellent ductility (approximate to 800% breaking strain) and relatively high breaking strength (approximate to 2 MPa). These discoveries elucidate an effective pathway to design smart inorganic/organic hybrid thermoplastic elastomers endowed with outstanding photochromic and mechanical properties as well as exceptional processability.