A Gemini-Type Supramolecular Amphiphile Based on a Water-Soluble Pillar[5]arene and an Azastilbene Guest and Its Application in Stimuli-Responsive Self-Assemblies.

Supramolecular amphiphiles are a type of intriguing building blocks to fabricate self-assembled nanostructures that can be applied in diverse fields. Gemini-type supramolecular amphiphiles, containing two hydrophobic tails and two hydrophilic head groups linked by a spacer, are good candidates to fabricate many advanced materials that are able to apply in surface modification, drug/gene delivery, and solubilization. Pillararenes, the fifth generation of macrocyclic host molecules, have been used to fabricate many supramolecular amphiphiles that played important roles in biomedical fields and materials science. However, compared with single-chain and bola-type supramolecular amphiphiles, the studies of gemini-type supramolecular amphiphiles based on pillararenes are very rare. Herein, a new strategy to prepare gemini-type supramolecular amphiphiles was reported. A new acid responsive host guest recognition motif in water on the basis of a 4,4'-azastilbene derivative (G1) and a water-soluble pillar[5]arene (WP5) was fabricated. The gemini-type supramolecular amphiphile was constructed by an azastilbene amphiphilic guest (G2) and WP5. Then its application in stimuli-responsive self assemblies was investigated. G2 self-assembled into nanoribbons in water. Upon addition of WP5, the gemini-type supramolecular amphiphile formed, leading to the formation of disklike micelles. After further addition of hydrochloric acid, the morphology changed into nanosheets.