EFFECT OF CHAIN LENGTHS OF N-ALCOHOL ON THE FORMATION OF SINGLE-PHASEMICROEMULSIONS IN N-HEPTANE N-ALCOHOL/SODIUM DODECYL SULFATE/WATER SYSTEMS/

To elucidate the effects of chain lengths of alcohols (1-butanol, 1-he xanol, and 1-octanol) as cosurfactants on the formation of a single-ph ase microemulsion (L-region) in n-heptane/n-alcohol/sodium dodecyl sul fate (SDS)/water systems, the phase diagrams of pseudoternary systems were determined under a fixed SDS/alcohol weight ratio (= 0.5). Conduc tivity, viscosity and light scattering intensity of the L-region were measured at 30 degrees C, and the results discussed from the microstru cture of these systems. Using the SDS-free model system, the distribut ion of alcohol and the interfacial tension between oil (heptane) and w ater phases were measured in the presence of alcohol. The difference i n distribution of alcohols resulting from differences in the chain len gths was found to be one of the key factors determining the extensions of the region of microemulsion and the microstructures. The L-regions in the hexanol and octanol systems were much smaller than in the buta nol system, The continuous phases of these systems were the oil-rich m edium (water-in-oh-type) throughout the L-region with increasing the w ater content. The L-region in the butanol system, on the other hand, w as larger and the continuous phases of this system changed gradually f rom the oil-rich to the water-rich medium (oil-in-water-type) through the bicontinuous medium (bicontinuous-type) with increasing the water content.