(307c) Stability and Interfacial Structure of Pickering Emulsions Stabilized by Nanoparticles

Particle-stabilized emulsions (Pickering Emulsions) are formed when small particles adsorb at the interface between the oil and water phases. The focus of this study is in the interfacial structure and stability of oil in water emulsions that are stabilized by silica nanoparticles. These Pickering emulsions are examined using a combination of small-angle x-ray scattering, dynamic light scattering and microscopy. Small-angle x-ray scattering provides the ability to examine the particle arrangement at the oil-water interface in situ. The particle organization at the interface can be correlated to the stability and drop coalescence of the emulsions. Dynamic light scattering and microscopy are used to quantitatively relate the oil droplet size and macroscopic stability of the emulsion to changes in the nano-scale structure. Pickering emulsions of micron sized particles are known to be sterically stabilized by close-packed microparticles that form an elastic shell. In contrast, nanoparticles are not close-packed at the oil-water interface and the emulsion is found to be electrostatically stabilized.