Random Interfaces and the Physics of Microemulsions
The structures of mixtures of amphiphiles, water and oil can sometimes show only microscopic correlations between the components (e.g. a three component solution) and sometimes exhibit long-range ordered structures (e.g. lyotropic liquid crystals). The term microemulsion in its most general use, connotes a thermodynamically stable, fluid, oil-water-surfactant mixture . In practice, microemulsions are taken to consist of structures with intermediate-range correlations. The oil and water regions are fairly well separated and the surfactant molecules are organized as monolayers at the internal water-oil interfaces. There are long-range correlations between the oil and water molecules in that they are separated on length scales of the order of hundreds of Angstroms. In addition, there are long range correlations among the surfactant molecules which self-assemble into a monolayer film at the set of internal water-oil interfaces. In this respect, microemulsions are different from three-component solutions. However, the set of interfaces which comprise the microemulsion do not show long range order comparable to that found in lyotropic liquid crystals, where there exists a periodic array of surfactant bilayers separating adjacent water or oil regions.
KeywordsPhase Behavior Surfactant Molecule Thermal Fluctuation Persistence Length Lamellar Phase
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