Relationship between high internal-phase Pickering emulsions and catastrophic inversion

An emulsion can undergo a catastrophic inversion from water droplets in oil to oil droplets in water driven by a change in the proportions of the two liquids. This can occur without hysteresis in particle-stabilized emulsions, an effect that was first systematically studied in emulsions of water and toluene stabilized by partially hydrophobic silica nanoparticles. Here we study experimentally how emulsions, comprised of these same ingredients, close to the composition at which inversion occurs respond to changes in the emulsification parameters and the quantity of particles. We argue that this inversion is driven by the flow properties of the phases under different mixing conditions. We thus identify the conditions under which a long-lived emulsion containing a high volume-fraction of droplets can form.