Article

Formation of highly swollen Lα-phases and vesicle phases from single chain surfactants by chemical reactions

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Abstract

Several general methods for the preparation of highly swollen lyotropic Lα-phases from single chain surfactants are described. It is shown that these Lα-phases can be prepared by mixing of surfactants with cosurfactants, by mixing of anionic and cationic surfactants, by combining ionic surfactants with hydrophobic counterions and surprisingly by mixing of Ca-salts of ionic surfactants with zwitterionic surfactants. Independently of their chemical composition the Lα-phases have several features in common:If the bilayers of the Lα-phases are ionically charged, and the phases are prepared by mixing of the components whereby the phases are exposed to shear forces, Lα-phases are obtained that have highly viscoelastic properties and consist of densely packed uni- and multilamellar vesicles. If, on the other hand, shear forces are avoided in the preparation, low viscous Lα-phases with stacked bilayers are obtained. Shear can be avoided when the phases are prepared with the help of a chemical reaction that produces one necessary component of the final phase in the stagnant fluid. Several reactions are described which can be used for the preparation of Lα-phases. It is shown that phase transformations to Lα-phases can be accomplished by the production of protons, of cosurfactants, or of ionic surfactants by chemical reactions. When the Lα-phases are produced by one of these reactions classic stacked bilayer phases are always obtained. These phases can easily be transformed to vesicle phases by exposing the Lα-phases to shear forces.

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