Associative Polymer-grafted Magnetic Nanoparticles for Stabilization and Recovery of Pickering Emulsions

Herein we introduce a smart Pickering emulsion fluid system, in which associative magnetic nanoparticles (AMNPs) are assembled at the oil–water interface to give magnetic-responsiveness to the emulsion drops. AMNPs are synthesized by grafting hydrophobically modified water-soluble poly(2-methacryloyloxyethylphosphorylcholine-co-stearyl methacrylate) onto silica-coated Fe₂O₃ nanoparticles (NPs) using surface-mediated living radical polymerization. Use of this synthetic protocol allows us to obtain AMNPs with a hydrophobically associative polymer layer with thickness of a few nanometers. We reveal that the AMNPs not only adsorb effectively on the oil–water interface due to the hydrophobic interaction, but also structurally stabilize the pickering emulsion due to the induction of electrostatic repulsion between droplets. Interestingly, we observe that the flow behavior of AMNPs-stabilized pickering emulsions is kinetically controllable in response to the applied magnetic field, thus demonstrating their practical applicability for magnetic-responsive enhanced oil recovery.