Ellipsometeric measurements have been performed to study the structure of the interfaces separating a microemulsion phase from its adjoining excess phases, these systems being usually referred to as a Winsor I, II and III. The surfactant (dodecylbetaine) used is a zwitterionic molecule. The most important results concern the diphasic systems. It is shown that the basic structure of their interfaces could be a mixed monolayer of surfactant and cosurfactant molecules. In Winsor I, an interfacial phase transition occurs, long before the Winsor III boundary; a monolayer of microemulsion droplets assembles in close association with the monolayer, retained at the interface by action of the forces invqlved in the D.L.V.O. theory. This layer is densely packed at the beginning of the Winsor III region, and the structure so formed disappears gradually inside this domain. In Winsor II such a transition is not detected. Either it does not occur, or it is situated very close to the Winsor III boundary where there are large fluctuations.
KeywordsInterfacial Tension Colloid Interface Aliphatic Chain Mixed Monolayer Thin Interlayer
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