Abstract
Structural change in hexagonal liquid crystal (H1) in the water/heptaoxyethylene dodecyl ether (C12EO7) system upon addition of mixed oil (m-xylene + decane) is investigated by phase study and small-angle X-ray scattering (SAXS). The surfactant layer curvature tends to be less positive or negative upon addition of the mixed oil at a high m-xylene/decane ratio, and the H1−Lα (lamellar liquid crystal) transition takes place. At a low m-xylene/decane ratio, however, the H1−I1 transition occurs with increasing mixed oil content, where I1 is a discontinuous micellar cubic phase. An excess oil phase directly separates from the H1 phase at a moderate m-xylene/decane ratio. The change in the effective cross sectional area per surfactant, aS, as a function of oil content was also measured at each mixing fraction of oils by SAXS. m-Xylene molecules tend to penetrate the surfactant palisade layer and widen aS, whereas decane molecules tend to be solubilized in the deep core of surfactant hydrophobic moieties and the...
Published Version
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