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

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.