Triple-Responsive Pickering Emulsion Stabilized by Core Cross-linked Supramolecular Polymer Particles

It is significant to explore multiresponsive Pickering emulsions because of their flexibility in terms of demulsification in comparison with the single stimuli-responsive systems. In this study, we described a triple-responsive oil-in-water Pickering emulsion that was stabilized by amphiphilic core cross-linked supramolecular polymer particles (CCSPs). For this purpose, beta-cyclodextrin-terminated poly(N-isopropylacrylamide) (PNIPAM-beta-CD) and azobenzene-capped poly(4-vinylpyridine) (P4VP-azo) were separately synthesized by reversible addition-fragmentation chain transfer polymerization. By virtue of the inclusion interaction between the beta-CD host and the azobenzene guest in dimethyl sulfoxide, the amphiphilic supramolecular block copolymer, poly(4-vinylpyridine)-b-poly(N-isopropylacrylamide) (P4VP-b-PNIPAM), was formed. CCSPs were prepared through the combination of the self-assembly of P4VP-b-PNIPAM in the selective solvent, water, and the cross-linking of the P4VP core with 1,4-dibromobutane. Due to thermoresponsiveness of PNIPAM shells and the supramolecular linkages between the cross-linked hydrophobic P4VP core and hydrophilic PNIPAM shells, the as-prepared CCSPs exhibited temperature-, light-, and amantadine hydrochloride guest-triggered morphological transitions. Such triple-responsive morphological transitions gifted CCSPs stabilized oil-in-water Pickering emulsion with flexible demulsification in response to various factors, such as thermo, light, and amantadine hydrochloride or their combinations. Such triple-responsive oil-in-water Pickering emulsion also provided an ideal platform for heterogeneous reactions conducted at the oil-water interface. A large interfacial area and responsive demulsification allowed the reaction to be performed with an efficient and sustainable pattern.