Visible-light-induced scission and rapid healing of polyurethane elastomers based on photoswitchable hexaarylbiimidazole units

Abstract

Smart materials based on photo-responsive dynamic covalent bonds have the potential for use in many applications, such as photo-modulated manipulators, actuators and self-healing materials. However, the development of high-performance multifunction visible-light-driven dynamic covalent systems has been insufficient. Herein, we report a novel linear polyurethane elastomer (HABI-PU) containing visible-light-switchable hexaarylbiimidazole (HABI) units in the polymer backbone with photo-induced scission and rapid healing capacities. When exposed to 405 nm light, the scratches on the HABI-PU film took only a few seconds to heal. More serious cut damage could be healed after exposure for 30 s and placed in the dark at room temperature for 6 h. Moreover, when a certain weight was loaded during light irradiation, the elastomers broke off as the toughness of the HABI-PU elastomers decreased. The reversible dissociation of the C–N bond of the HABI units caused the scission of long polymer chains into short chains upon light irradiation and further endowed HABI-PU with the properties of photo-induced fracture/healing. Such elastomers are promising for application in the fields of photo-controlled triggers, biomimetic systems, recycled materials, optical machining, and other engineering streams.