A structural description of liquid particle dispersions: Ultracentrifugation and small angle neutron scattering studies of microemulsions

Abstract

Microemulsions are colloidal systems which are made by a dispersion of minute droplets (a few hundred Å in diameter) of one component (e.g. water) in a continuous medium formed by another immiscible component (e.g. oil); the droplets are surrounded by a mixed film of surfactants. New information has been obtained about the distribution of the various components in the elementary droplet. The hydrodynamical interface is shown to contain an important amount of the continuous phase and a quantity of alcohol which increases with the amount of solubilized water. In contrast, the corresponding variation of the area per polar head of the surfactant molecule is relatively small. Small angle neutron scattering indicates that a portion of the interfacial film, 9 Å thick, is not penetrated by the oily phase. The droplets are weakly correlated.