Lyotropic Mesophases of a Fluorinated Surfactant with a Short Nonionic Polar Head in Water

The phase behavior of a water−nonionic fluorinated surfactant C6F13C2H4SC2H4(OC2H4)2OH system is reported here. Beyond a reverse micellar phase, three other mesophases are found: a lamellar phase Lα, a bicontinuous cubic domain V2, and a sponge phase L3. Its phase diagram is compared with hydrogenated ones. The characterization of these phases and the determination of their structural parameters are performed by SAXS experiments. The cubic phase domain is divided into two cubic phases corresponding to the Ia3d and Pn3m structures. They both are described according to ICR and IPMS models. The study of the structural parameters shows that the area per polar group stays constant and the hydrophobic surfactant part is unchanged in all the liquid crystal domains. Epitaxial relationships between the phases are discussed.