Effect of Hydrogen Bond on the Performance of Organic Gel Based on Sterically-Hindered Diarylethenes

Photo-responsive organic functional gels have drawn the increasing attention due to their functional diversity. Based on sterically-hindered diarylethenes, we synthesized two photoresponsive organic gels, ap-BAM and ap-YJ , which exhibited reversible fluorescence and gelation properties upon light irradiation. Both organic gel materials show high conversion ratio and fatigue resistance in the solution state. Meanwhile, ap-BAM with hydrogen-bonding network can convert into the gel state at room temperature, and the reference system of ap-YJ can only convert into gels at a low temperature (−10 ℃). In addition, due to the aggregation-induced emission (AIE) property of the sterically hindered diarylethene core, the open form of the gel exhibits a relatively strong fluorescence. Upon irradiated by UV light, two photoresponsive gels transfer from gel to solution state along with a quenched fluorescence. This can be attributed to an increase in the rigidity of the closed form and a steric hindrance of the methyl groups, which diminishes intermolecular interactions. The morphology of the gels is characterized by scanning electron microscopy (SEM). A denser gelatin with three-dimensional porous network can be found in ap-BAM system. However, ap-YJ forms just a dense film, indicating that the hydrogen-bonding network in the ap-BAM gel system facilitates the gelation.