Mixtures of branched non-ionic oligo-oxyethylene surfactants in aqueous solutions — the effect of molecular geometry on LC phase behaviour 4 |
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Authors: | K Kratzat C Stubenrauch H Finkelmann |
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Institution: | (1) Institut für Makromolekulare Chemie, Universität Freiburg, 8 tefan-Meier-Str. 31, 79104 Freiburg i. Br., FRG |
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Abstract: | The LC phase behavior of ternary mixtures of the two corresponding branched non-ionic surfactants 1,3-bis-(methoxy-tetraoxyethylene)-2-propoxy-tetradecane (Y-surfactant) and 1,3-bis-(heptyloxy)-2-propoxyoctaoxyethylene mono-methyl ether (V-surfactant) and water were studied by polarizing microscopy. The two branched surfactants, which have different molecular geometries but nearly the same hydrophilic-lipophilic volume ratio, exhibit extremely different phase behavior in binary surfactant/water systems. For the ternary mixtures of Y- and V-surfactant and water we found-according to established packing models-a continuous stabilization of the cubic and hexagonal phases and a destabilization of the lamellar phase with increasing amount of Y-surfactant. On the other hand, we observed a thermal stabilization of the lamellar phase. The maximal transition temperatures of the lamellar phase pass a maximum with increasing amount of Y-surfactant. |
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Keywords: | Non-ionic surfactants oligo-oxyethylene surfactants mixtures of surfactants lyotropic liquid crystal phase behavior |
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