PHASE BEHAVIOR AND QLS IN POTASSIUM LINOLEATE/n-ALKANOL MICROEMULSIONS

ABSTRACT

We present here pseudo-ternary phase maps of three surfactant stabilized quarternary systems composed of water, hexadecane, potassium lincleate (KL) as surfactant and the three saturated primary alcohols, 1-butanol, 1-pentanol and 1-hexanol as cosurfactants. These systems exhibit phase behavior analogous to that of the potassium oleate/n-alkanol systems recently reported. Butanol gives a system with one large single phase region extending from the water side to the oil side of the diagram. Pentanol yields two areas of single phase; a large upper w/o region, and a smaller finger-like o/w region arcing up from the water apex to ca. 20% emulsifier. The hexanol system reveals the largest expanse of the w/o region, but in the water continuous corner only a metastable clear area was encountered. Quasielastic Light Scattering (QLS) measurements are also reported in all three systems and an attempt is made to correlate these measurements to the phase behavior. The butanol system gave no QLS evidence of aggregation at three different compositions. The pentanol and hexanol system gave diffusion coefficients that suggest the existence of aggregates with correlation lengths in the 100 to 700 Å range. In general, diffusion coefficients for the hexanol System were smaller than those at comparable compositions in the pentanol system. In all three systems at low water content (<20%) in the single phase region near the E-D axis, QLS gives no evidence of aggregation. Finally, we report that diffusion coefficient measurements at compositions near phase boundaries in the pentanol and hexanol systems gave low values which were interpreted as manifestations of proximity to critical points.