Self-assembly Of Photoresponsive Nanoparticle Surfactants At Water-oil Interfaces

Nanoparticle and polymer ligands can form nanoparticle surfactants in situ at the water-oil interface by electrostatic self-assembly,their assembly and jamming transition process at the liquid-liquid interface provides new opportunities for the preparation of all-liquid devices such as microcapsules,bicontinuous interfacially jammed emulsion gels,and structured liquid.Most of the current studies are based on the electrostatic force between carboxyl-amino ion pairs to realize the self-assembly of nanoparticles at the water-oil interface,and the interfacial assembly behavior of nanoparticle surfactants is regulated by adjusting the pH value or ionic strength,and the responsiveness is relatively simple.In this study,we take advantage of the recognition of cyclodextrin host molecule and azobenzene guest molecule to make nanoparticles self-assemble at the water-oil interface to form photoresponsive nanoparticle surfactants,and the interfacial activity is adjusted by changing the concentration of water and oil phases,at the same time,based on the photoisomerization of azobenzene,the assembly of nanoparticles surfactant at the water-oil interface is regulated by the transformation of visible light and ultraviolet light,a simpler and more convenient way of regulation is explored.The surfactant is further used to prepare stable photo-responsive microcapsules based on the Pickering emulsion template method,and the encapsulation of small molecule fluorescent dyes is successfully achieved,and the size of microcapsules is controlled by changing the concentration and proportion of water and oil.The photoresponse of azobenzene is used to regulate the jamming and unjamming behavior of nanoparticle surfactants at the water-oil interface to realize the photo-controlled release of small molecules from microcapsules.In addition,the structured liquid can be prepared by the jamming transition of nanoparticles at the water-oil interface.Under UV light irradiation,the structured liquid can be deformed while the supramolecular surfactant is disassembled,and a new type of photoresponsive structured liquid is constructed.These new microcapsules and liquid devices provide new strategies for future applications in microreactors and drug packaging.