On the Structure of Five-Component Microemulsions
A family of 5-component microemulsions made with sodium 4-(1’-heptylonyl)-benzenesulfonate, iso-butyl alcohol, dodecane, and NaCl brines of various concentrations has been studied with small-angle neutron scattering (SANS) and quasielastic light scattering (QLS) methods. Both techniques show that when the water volume fraction, ФW, is either less than 0.20 or greater than 0.75, the size of the well-defined droplets (water in oil or oil in water) increases nearly linearly as the volume fraction of the dispersed phases increases. The water in oil droplets are spherical and polydispersed in size, while the oil in water droplets are prolate with an aspect ratio of approximately 3:1. For the intermediate aqueous volume fractions between 0.20 and 0.75, both the QLS and SANS results indicate that the length scales in the microemulsion phase vary approximately in proportion to Ф(1 − ФW). These observations favor a model of bicontinuous structure in the intermediate regime.
KeywordsApparent Diffusion Coefficient Scatter Length Density Microemulsion Droplet Water Volume Fraction Microemulsion Phase
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