Bis-p-Sulfonatocalix[4]arene-Based Supramolecular Amphiphiles with an Emergent Lower Critical Solution Temperature Behavior in Aqueous Solution and Hydrogel.

An unexpected lower critical solution temperature (LCST) phenomenon is observed in a bis-p-sulfonatocalix[4]arene-based supramolecular amphiphile system, and the mechanism of this intriguing phenomenon is studied. The unusual macroscopic thermoresponsive behavior is based on the switch of the system from water-soluble assemblies to insoluble netlike cross-linked nanoparticles under temperature stimulus, which is regulated by multiple weak interactions, including hydrophilic and hydrophobic interactions, π-π stacking, and host-guest recognition. By using the LCST solution as the dispersion medium, a hydrogel with LCST behavior can be fabricated. This work contributes toward better understanding about calixarene-induced aggregation (CIA) and thermoresponsive self-assembled systems. It will also help to enrich the designing of complexed supramolecular amphiphile systems and develop their potential applications in hydrogels.