THE ISOTROPIC OIL SURFACTANT-RICH PHASE IN SYSTEMS OF AROMATIC OILS, NONIONIC SURFACTANTS, AND WATER

The different structures in the isotropic oil-surfactant-rich phase co mposed of aromatic oils, nonionic surfactants, and water have been elu cidated by means of conductivity, viscosity, and light-scattering meas urements at 298.2 K. The oils used are benzene and 1,3,5-trimethylbenz ene and the surfactants used are commercial nonyl phenyl polyethoxylat es. The oils and surfactants are completely soluble in each other. At low surfactant contents water is sparingly soluble in the oil-surfacta nt mixtures, indicating that aggregates solubilizing water are not for med. As water is added to mixtures of intermediate mass fractions of o il and surfactant, closed aggregates solubilizing water are formed. At high surfactant contents, open structures are formed and the solubili ty of water depends on the surfactant used. As the nonionic surfactant s are mixed with the anionic surfactant sodium 1,4-bis (2-ethylhexyl) sulfosuccinate (AOT), closed aggregates solubilizing water are also fo rmed at low surfactant contents and the open structures are still pres ent at high surfactant contents. (C) 1995 Academic Press, Inc.