AIE gel exhibiting continuous gradient fluorescence based on a polar‐responsive AIE‐gen

Abstract

Traditional multicolor fluorescent hydrogels are generated through the assembly of discrete fluorescent hydrogels, which is not a complete integration much distinct from living organisms. On the basis of aggregation‐induced emission (AIE), a special solvent polar‐responsive AIE molecule possessing a twisted intramolecular charge transfer (TICT) effect was noticed. By incorporating it into the gel network, an AIE gel that displays continuous gradient fluorescence was fabricated. First, hydrogel A containing the solvent polar‐responsive AIE‐gen was prepared to show orange fluorescence. After soaking in the organic solvents, the fluorescence color transition of hydrogel A ranging from orange to green occurred when being immersed in high‐polarity organic solvents ascribed to the embedded AIE‐gen owning TICT effect. Then, hydrogel A was successively lifted up from organic solvents. Due to the different immersion time of each section for the hydrogel, the polarity difference occurred. Then, the produced gel B showed continuous gradient fluorescence ranging from orange to green under the irradiation of UV light.

Stimuli‐responsive fluorescent hydrogels: Strategies and applications

“…[32] Controlling the degree of aggregation of AIEgens (luminogens exhibiting AIE attributes), mostly by modulating the solvent polarity, can adjust the intensity or color of fluorescence, making AIEgens a type of convenient dynamic motif in the design of dynamic fluorescent hydrogels. For instance, Tang [62] recently reported a multicolor hydrogel that can display sequential gradient fluorescent colors (Figure 3). A water-soluble AIEgen triphenylamine vinyl pyridine acrylate was covalently embedded into polymer networks to obtain hydrogels showing polarity-dependent emission.…”

“…[67] In 2019, Hu and coworkers [68] created F I G U R E 3 Schematic representation of (a) the solvent-responsive multicolor fluorescent hydrogel and (b) the fabrication process of the hydrogel to show gradient fluorescence. [62] Reproduced with permission.…”

High-Molecular-Weight Poly[2]catenanes Prepared by Hydroxyl-Alkyne Click Chemistry

“…Therefore, it seemed feasible to further replace M2 with another diacetylene molecule containing functional groups in order to prepare functional poly[2]­catenanes. Here, TPE unit was selected as the functional group to be incorporated into diacetylene due to its aggregation-induced emission (AIE) effect, − which could be used to prepare fluorescent poly[2]­catenanes. 1,2-Bis­(4-hydroxyphenyl)-1,2-stilbene was functionalized by propiolic acid to form M3 , with which M1 could react to obtain poly([2]­catenane- alt -TPE) (Figure a, Scheme S3).…”