In-Situ Asymmetric Surface Functionalization of Silica Nanoparticles in Pickering Emulsion

Pickering emulsions are emulsions of any type, for example oil-in-water (o/w) or water-in-oil (w/o), stabilized by solid particles in place of surfactants.

This study presents Pickering emulsion formation of various aprotic, nonpolar solvents, generated by templating o/w droplets stabilized by silica/poly(organosiloxanes) particles, via interfacial reaction of organosilanes.

Amphiphilic silica particles that are able to assemble at the phase boundary of the dual-phase mixture of water and immiscible organic solvent were prepared by interfacial silanization of their surface hydroxyl groups with two different alkoxysilanes. A shell structure around the emulsion droplets was formed, with the two ligands contributing equally to its formation. The resulting homogeneous emulsions were creamy and stable over several weeks. A silica-polysiloxane network, responsible for the shell formation and bridging in-between the droplets was observed. After evaporation of the liquid phases, a porous, honeycomb-like hierarchical architecture was generated with spherical cavities, whose size and shape can be tuned according to the organic solvent in use.