Temperature-induced reversible transition between vesicle and supramolecular hydrogel in the aqueous ionic liquid-β-cyclodextrin system.

The vesicle is found to form in the concentrated aqueous solution of ionic liquid 1-dodecyl-3-methylimidazolium bromide (C(12)mimBr) and β-CD. By decreasing the temperature, the vesicle changes into a novel supramolecular hydrogel constructed from lamellae. The process is reversible and reproducible. The mechanism for the formation of vesicles and supramolecular hydrogel is studied by various methods. It is suggested that the main driving force is hydrogen bonding between β-CDs, β-CD and the solvent, the imidazolium headgroup of C(12)mim(+), and the solvent. Accordingly, the basic structural features of the vesicle and supramolecular hydrogel based on ionic liquid and β-CD are illustrated. The structural evolution from vesicles to hydrogels is also discussed herein.