Formation and Stability of Emulsions: Effect of Surfactant-particle Interactions and Particle Shape

Formation and stability of emulsions is one of the important topics in the field of colloids and interfacial science. Surfactants and colloidal particles are often used to stabilize emulsions. Surfactants are amphiphilic molecules; they minimize the energy required for the emulsion formation by reducing oil-water interfacial tension. Colloidal particles are not amphiphilic, but partially wettable particles favors the adsorption at oil-water interface with a desorption energy well above thermal energy. With sufficient coverage at the interface, they act as barriers against droplet coalescence and enhance the emulsion stability. In this work, the response of particlestabilized (Pickering) emulsions to the addition of different surfactant solutions and the stability of surfactant stabilized emulsions to the addition of particle suspensions were studied. There were different end points for emulsion droplets and different particle release modes for Pickering emulsions depending upon the interactions between surfactants and particles, surfactant-particle ratio, and mixing conditions. The effect of particle shape on the formation of Pickering emulsions is also studied. It is found that the inter-particle interactions and particle shape play major role in determining the microstructure and final stability of the emulsions. The combinations of optical, confocal, and Cryogenic scanning electron microscopy were used to determine the final stability and structure of the emulsions.