Effect of Nanoparticle Wettability on the Stability and Coalescence of Pickering Emulsions

Solid-stabilized emulsions, i.e. Pickering emulsions, strongly resist coalescence, even in high-temperature, high-salinity conditions where conventional surfactant-stabilized emulsions would fail. Pickering emulsions are promising candidates for applications in porous media, such as enhanced oil recovery and aquifer treatment. Pickering emulsion stability and coalescence rely on fluid-particle interactions that depend on a variety of particle characteristics, including wettability; however, the role of wettability is not well understood. To determine the effect of wettability, this work examines emulsions stabilized by silica nanoparticles coated with two similarly sized molecules with different hydrophilicities: (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and [3-(2,3-dihydroxypropoxy)propyl]trimethoxysilane (GLYMO). We characterized the particle size and surface (zeta) potential of the coated nanoparticles and generated oil-in-water emulsions with a tip sonicator. Emulsion stability was quantified by observations of microchannel flow and by centrifugation.