Research on Reversible Wetting Regulation and Interfacial Adaptive Behavior of Multi-Stimulus Responsive Nanoparticles

Abstract Stimulus-responsive nanomaterials with reversibly switchable wettability are promising for separation and interfacial engineering. Here, polymer-modified silica nanoparticles (Si@(MO)NPs) grafted with MEO2MA-co-OEGMA were synthesized, showing dual salt- and acid-responsive wettability switching. High ionic strength induces dehydration and collapse of the polymer shell, switching wettability from hydrophilic to oleophilic and driving migration to the oil phase or interface; subsequent acid stimulation protonates carboxyl groups, restoring hydration and chain extension and enabling reverse migration to the aqueous phase. Molecular dynamics simulations show that increasing salt concentration reduces polymer–water hydrogen bonding and the radius of gyration while enhancing mobility toward the oil phase, whereas 5 wt % citric acid optimizes protonation, stabilizes extended chain conformations, and improves interfacial hydration and diffusion. These results establish a coupled hydration-conformation regulation mechanism for designing multistimuli-responsive nanomaterials.