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

The phase behavior of a water−nonionic fluorinated surfactant C 6 F 13 C 2 H 4 SC 2 H 4 (OC 2 H 4 ) 2 OH system is reported here. Beyond a reverse micellar phase, three other mesophases are found: a lamellar phase L α, a bicontinuous cubic domain V 2, and a sponge phase L 3 . 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 Ia 3 d and Pn 3 m 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.