Dynamics of Spontaneous Emulsification for Fabrication of Oil in Water Emulsions

We present an experimental study of the dynamics of spontaneous emulsification when a surfactant solution in oil is brought into contact with pure water. Direct visualization using phase contrast microscopy shows that vesicles (closed bilayer structures) form in the oil phase near the interface with the water and explode, thereby pulverizing oil droplets into the aqueous phase. The results thus show the importance of the presence of bilayer structures in the spontaneous emulsification process for the formation of oil-in-water emulsions. Measurement of the droplet size distribution shows that an optimal ratio of surfactant to cosurfactant exist. It is shown that both the microscopy observations and the size of the droplets can be related to the nonequilibrium water/oil interfacial tension just after the two phases have been brought into contact.