Controlling the formation of particle-stabilized water-in-oil emulsions

We apply the versatile method of in situ hydrophobization of aluminum oxide particles with short amphiphiles for the stabilization of water-in-toluene emulsions. We found that octyl gallate is an ideal surface modifier to adjust particle wetting properties in toluene. The most important parameters affecting the droplet size were investigated including particle size and wetting properties, particle concentration, emulsion composition, and shear rate. The median droplet size ranged between 2.6 and 80 μm in this study. The results are discussed to shed light on the underlying processes controlling the droplet size. It was found that emulsion formation is either rupture or coalescence controlled, which is in close analogy to the mechanisms reported for surfactant-stabilized emulsions.