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 are potential for many applications such as photo-modulated manipulators, actuators and self-healing materials. However, the development of high-performance multifunction visible light-driven dynamic...

Photomechanical polymer hydrogels based on molecular photoswitches

“…Li and coworkers 105 synthesized polyurethane elastomer HABI‐PU containing photo‐responsive HABI by facile one‐pot copolymerization of dihydroxy‐functionalized 2‐(2‐hydroxyethoxy) hexaarylbiimidazole (2‐glycol‐HABI) with hexamethylene diisocyanate (HDI) and polytetrahydrofuran glycol (PTMG 1000 ) (Figure 9A). The scratch on the transparent HABI‐PU film could be rapidly healed in 30 s upon 405 nm (325 mW cm −2 ) laser irradiation (Figure 9B).…”

“…The scratch on the transparent HABI‐PU film could be rapidly healed in 30 s upon 405 nm (325 mW cm −2 ) laser irradiation (Figure 9B). 105 This is attributed to the reversible cleavage of HABI units in HABI‐PU under light irradiation to form two discrete TPIR's, resulting in shorter polymer chains and higher chain mobility. After the removal of light, the TPIR's between the two cross‐sections collided and combined into HABI again to achieve healing.…”

“…After the removal of light, the TPIR's between the two cross‐sections collided and combined into HABI again to achieve healing. For a more serious cut wound on HABI‐PU trip (3.6 × 0.38 × 0.22 cm 3 ), 95% of the initial strain can be recovered after illumination for only 20 s and then standing in the dark for 6 h 105 . The photoresponsive properties of dynamic covalent bonds can not only adjust the length and mobility of polymer chains, but also change the crosslinking density of materials, which will be beneficial to the design and preparation of photoresponsive hydrogels with self‐healing properties.…”

“…(B) Self‐healing photographs of HABI‐PU and schematic diagram of structure changes of polymer chain in HABI‐PU. Reproduced with permission 105 . Copyright 2021, Royal Society of Chemistry.…”

Photo-stimuli-responsive Organic Room-Temperature Phosphorescent Materials

“…Hexaarylbiimdazole (HABI) is a famous photosensitive molecule that can fragment into two colored 2,4,5-triphenylimidazoyl radicals by homolytic cleavage of carbon–nitrogen bonds and recover to the initial state by heating. − Recently, Ma et al developed two HABI ( 54 and 55 ) polymers, which exhibited phototunable RTP properties (Figure A). Their RTP intensities gradually decreased with continuous UV irradiation and could recover to their initial state after heating .…”