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.

Automated summary

Core/shell PVSt-b-PS@Fe3O4 composite nanoparticles are achieved by grafting living cationic block copolymer chains onto the surface of amine-capped Fe3O4 NPs, with the number of grafted chains controlled by the molecular weight of PVSt-b-PS. The resulting (PVSt-g-PEG)-b-PS@Fe3O4 composite NPs, after PEG grafting via a click reaction, exhibit high dispersibility in water. When oil is added to the aqueous dispersion, the composite nanoparticles organize dynamically and eventually stabilize into a Pickering emulsion.