X-ray Diffraction Study of a Three-Component Lamellar Phase

Three-component lamellar phase has been investigated which consists of C12E5, oc-tane and water. This is a layered phase, the lyotropic equivalent of a thermotropic smectic-A phase. X-ray scattering techniques were used on powder and aligned sam-ples, as well as the optical microscopy investigations to understand the structure and the interactions that govern this lyotropic system, and also the temperature depen-dence of such important parameters as layer-periodicity, the layer thickness and the exponent 77 which characterizes quasi-long range order. Experiments were done with various surfactant concentrations and oil/water volume ratios. The system was chosen for two reasons. First of all, a lamellar phase continuously exists from an oil-rich through an equal oil-water to a water rich region in the ac-cessible temperature range (- 33oc). Also the lamellar phase continue to exist with the wide range of the surfactant concentrations, which allowed us to study the dilu-tion of the lamellar phases. Secondly. since it is a nonionic surfactant. there are no electrostatic interactions present in this system, i.e. it is a purely sterically stabilize