Photoresponsive Hexaarylbiimidazole‐Crosslinked Hydrogels: From Synthesis to Diverse Applications

Abstract The development of light‐sensitive hydrogels with rapid and on‐demand responses stands represents an important outstanding challenge for developing flexible devices. Here, a light‐sensitive divinyl monomer, bis(2‐methacrylamidoethyl) 4,4′‐(4,4′,5,5′‐tetraphenyl‐2′H‐[1,2′‐biimidazole]‐2,2′‐diyl)dibenzoate (HABI‐diMAm), was synthesized and further copolymerized with N‐(hydroxymethyl)acrylamide (N‐MA), leading to the formation of a photoresponsive single network hydrogel (G1) that undergoes a reversibly dynamic transformation from gel to sol upon 405 nm light irradiation, enabling a flexible non‐contact dynamic information display system. With the introduction of an additional permanent covalent crosslinker, a dual‐crosslinked single network hydrogel (G2) was developed as a flexible actuator that responds to light‐irradiation within seconds. Next, X‐ray‐activated persistent luminescent nanoparticles (X‐PLNPs) were incorporated into the dual‐crosslinked single‐network network hydrogel, leading to hybrid hydrogel (G3) that acted as a flexible X‐ray scintillator screen with light‐controlled self‐fitting properties on non‐planar substrates. The X‐ray imaging results demonstrated successful recording of clear images that precisely reflect the real defects in the targeted non‐planar object. Hence, the introduced HABI‐crosslinked hydrogels have broad potential as photoresponsive hydrogels.