Stabilization of emulsions by fine particles I. Partitioning of particles between continuous phase and oil/water interface

Some of the physicochemical mechanisms governing the stability of oil/water emulsions in the presence of fine particles are investigated. The thermodynamics of particle partitioning between a continuous aqueous phase and the oil /water interfaces of the emulsion droplets is analyzed. An isolated particle with an appropriate three-phase contact angle is trapped in a deep energy well at the interface of an oil/water emulsion droplet. This is consistent with the experimental observations that a close-packed two-dimensional structure of particles is formed on the oil/water interfaces of emulsion droplets stabilized by particles. In equilibrium partitioning the energy depth of a single interfacial particle should be balanced by net repulsive interactions between neighbouring particles on the interface. Electric double layer and short-range salvation and solid elastic forces between the interfacial particles are found to be insufficient to provide the required large repulsive interaction.