Mesomorphic polymorphism of binary mixtures of water and surfactants

Abstract

In this work, a vector lattice model is employed to study binary mixtures of water and surfactants. The face-centered-cubic lattice is employed in order to best approximate a realistic liquid environment. The model is analyzed by low-temperature expansion and Monte Carlo methods. It is shown that for sufficiently strong surfactant-water interactions 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 lamellar phases as well as the inverse bicontinuous cubic, inverse hexagonal and inverse micellar cubic phases are stable in the model. It is shown that the inverse bicontinuous cubic structure in our model is remarkably similar to the gyroid phase. The formation of water channels in the surfactant bilayers of a lamellar phase is also examined.