MESOMORPHIC POLYMORPHISM OF BINARY-MIXTURES OF WATER AND SURFACTANTS

In this work, a vector lattice model is employed to study binary mixtu res of water and surfactants. The face-centered-cubic lattice is emplo yed in order to best approximate a realistic liquid environment. The m odel is analyzed by low-temperature expansion and Monte Carlo methods. It is shown that for sufficiently strong surfactant-water interaction s the system exhibits a rich polymorphism where up to eight phases are stable. In addition to the disordered water-rich and surfactant-rich phases, liquid-crystalline phases such as the hexagonal and the lamell ar phases as well as the inverse bicontinuous cubic, inverse hexagonal and inverse micellar cubic phases are stable in the model. It is show n that the inverse bicontinuous cubic structure hi our model is remark ably similar to the gyroid phase. The formation of water channels in t he surfactant bilayers of a lamellar phase is also examined.