Spontaneous emulsification through surfactant hydration : the PIT and PIC methods revisited

Because oil and water do not mix on the molecular scale, dispersions of oil in water require energy. Usual methods to produce nano-emulsions require high shear rates and loads of surfactants. However very small droplets of oil in water can be obtained, if the interfaces’ curvature matches the curvature the surfactant layer would like to adopt, due to the asymmetry between its hydrophilic and hydrophobic part. Such equilibrium systems (called microemulsions) suffer many disadvantages, such as the important amounts of surfactants required and the size range that can be obtained. The aim would be to design emulsions in a larger range, without high energy input and using the triggers as for microemulsions.

This presentation will focus on the systematic investigation of two well know emulsification methods : the Phase Inversion Temperature (PIT) and the Phase Inversion Composition (PIC) processes. The main findings are that it is actually useless to undergo phase inversion and in each case we identified an important access state which determines the final emulsion. However those access states differ in geometry between the PIT (spheres) and the PIC (bicontinuous). Consequences are that the two methods are intrinsically different and we demonstrate that the PIT method is more efficient in the use of the surfactant than the PIC method and offers the opportunity to prepare superswollen microemulsions that can be put in a metastable state.