Microemulsions, lyotropic liquid crystals, and other association structures

Phase diagrams have been determined showing the extent of the inverse micellar or microemulsion region for several ionic surfactants and some cosurfactants. Hexylamine has been found to be a very effective cosurfactant giving rise to very good water solubilizing capacity at extremely low surfactant concentrations and very low cosurfactant levels at rather high initial hydrocarbon levels. A fairly extensive study of phase equilibria of the system composed of sodium dodecyl sulfate, hexylamine, heptane, and water has been carried out. The conductivity behavior of the inverse micellar or microemulsion phase of the system shows the percolation phenomenon. Low angle X-ray diffraction has been used to investigate the lamellar liquid crystalline phase. Equations are developed or modified to allow determination of the degree of interpenetration between the amphiphile bilayers and aqueous layers in the lamellar liquid crystal structure. The association structures of water-in-oil (W/O) microemulsions containing sodium dodecyl sulfate, hexylamine, heptane, and aqueous sodium chloride have been investigated using time-average and dynamic light scattering techniques. Molecular weights, diffusion coefficients, and particle size of microemulsion droplets were determined. Modern theories of fluids have been used to interpret the behavior of scattered light intensity and diffusion coefficients --Abstract, page iii