Responsive Self-Assembly of Supramolecular Hydrogel Based on Zwitterionic Liquid Asymmetric Gemini Guest

Graphical Flick the switch ! A reversible sol–gel phase transition of a prepared supramolecular hydrogel can be triggered by light and temperature. UV irradiation changes the mode of inclusion in the complex formed between β-CD and the azobenzene, whereas thermal treatment influences the hydrogen bonding between β-CD and bis(trifluoromethanesulfonyl)imide (see figure). A low-molecular-weight supramolecular hydrogel has been fabricated based on host–guest interactions between β-cyclodextrin (β-CD) and an asymmetric gemini zwitterionic liquid (ZIL) containing an azobenzene and bis(trifluoromethanesulfonyl)imide. Reversible sol–gel phase transitions were triggered by light and temperature. The binding stoichiometry, mainly noncovalent interactions in the hydrogel, photo- and thermoresponsive mechanisms, and mode of inclusion in the complex were studied in detail by NMR spectroscopy, UV/Vis spectroscopy, isothermal titration calorimetry, and control experiments. Interestingly, the β-CD in the complex can be photo-manipulated to shuttle along the guest molecule, accompanied by a change in the circular dichroism signals. Reversible switching of the conductivity accompanies the sol–gel phase transition, which demonstrates the stability of the supramolecular hydrogel and its potential application in multi-stimuli-responsive electric sensor materials.