The stepwise organization of nanoparticles into a Pickering emulsion

Core/shell PVSt-b-PS@Fe₃O₄ composite nanoparticles (NPs) are achieved by grafting living cationic block copolymer chains onto the surface of amine-capped Fe₃O₄ NPs via fast termination. The number of chains grafted can be tuned via the molecular weight of PVSt-b-PS. Upon grafting PEG onto the PVSt block via a click reaction, the resulting (PVSt-g-PEG)-b-PS@Fe₃O₄ composite NPs become highly dispersible in water. A composite nanoparticle with ten chains is selected as a homogeneous NP to demonstrate the dynamic stepwise organization of the NP as oil is fed into the aqueous dispersion. The individual NPs with captured oil are further aggregated, but remain stable with increasing oil content. Eventually, a Pickering emulsion forms in which the aggregates are anchored at the emulsion interface. This dynamic behavior study helps to provide an understanding of the mechanism by which NPs stabilize Pickering emulsions.