Photochromic behavior of naphthopyran in styrene–butadiene–styrene elastomer thin films: Effect of stretching of film and linker

Thermoplastic elastomers of styrene–butadiene–styrene (SBS) triblock copolymers containing grafts of naphthopyran as side‐chain polymer were prepared by polymerization of naphthopyran acrylate monomer with a solution of SBS in tetrahydrofuran. Thin films of all grafted SBS polymers displayed photochromism, the decoloration kinetics of naphthopyran in the films was modeled by fitting biexponential equations to the photochromic decay curves after UV light irradiation. Stretching of the grafted SBS film at room temperature affected the fading rate constant k1 of the naphthopyran. The length of linker between photochromic naphthopyran moiety and the acrylate unit in monomer also affected the fading rate constant k1 of the naphthopyran in SBS elastomers. This study presents an example of tuning the photochromic properties of naphthopyran via two approaches, polymer structure, and stretching of films.