Transport properties of micellar solutions and microemulsions.

Binary nonionic surfactant-water systems were studied prior to the more complex nonionic surfactant-water-oil systems. Phase diagrams were determined for the tetraoxyethylene dodecylether (C[12]E[4])-water and the Brij 30-water systems; the available hexaoxyethylene dodecylether (C[12]E[6])-water phase diagram was confirmed.Conductivity measurements were made in the isotropic liquid regions of these systems and self-diffusion measurements were made in the isotropic liquid regions of the C[12]E[4]-water and C[13]E[6]-water systems, in order to elucidate the structures of these regions. Self-diffusion measurements were made by the NMR spin-echo method with a pulsed field gradient using the nucleus 1H. The results indicated that the surfactant is aggregated and water plus oxyethvlene chains form the continuum up to 100% surfactant. Phase diagrams were determined for the C[12]S[4]-H[2]O-heptane system and the Brij 30-H[2]O-hexane system. Conductivity measurements were made in the isotropic liquid regions. The existence of both water-continuous and oil-continuous isotropic liquid regions is confirmed. The possibility of a percolation mechanism leading to high conductivities in oil-continuous samples is discussed as is phase inversion within the isotropic liquid region, at 1owt water content. The effect of different hydrocarbons on the phase behaviour at low surfactant content was studied by means of phase diagrams and conductivity measurements. The conductivity results at low surfactant content are interpreted in terms of water-continuous and oil-continuous structures and also bicontinuous structures via wrhich phase inversion can occur. Phase diagrams were determined for C[12]E[4]-H[2]O-triacetin and Brij 30-H[2]0-triacetin. The differences between these systems and those with heptane and hexane as third components are explained on the basis of the different structure and polarity of the triacetin molecule.