A Structural Study of Two Oxyethylene Alkyl Ether-Water Mesophase Systems in the Presence of Small Amount of Sodium Dodecyl Sulphate, SDS Ionic Surfactant

Abstract

Abstract Two structural studies of the following two liquid crystals systems: [(C12EO4 + 1% SDS)/H2O, ca. 25–85 wt.% surfactant] and [(C12EO8 + 1% SDS)/H2O, ca. 40–71 wt.% surfactant] have been investigated. Both previous systems contain similar amount of Sodium Dodecyl Sulphate, SDS. It has been found that there are two mesophases at 25°C: the lamellar Lα and the hexagonal H1. Their structural parameters were determined using small angle X-ray scattering (SAXS) patterns. The mesophases study of the Lα and H1 regions allows the evolution description of the surfactant chains conformation. The geometrical parameters of the Lα and H1 mesophases such as the thickness of hydrocarbon core of the lamellar mesophase and the diameter of rods forming the hexagonal structure were calculated. In the lamellar, Lα and the hexagonal, H1 mesophases, the surface area per molecule and the thickness of the hydrocarbon core exhibited a little sensitivity change toward concentration. The thickness of the ethoxy groups was estimated in Lα and H1 mesophases as a function of surfactant concentration in (C12EO4 + 1% SDS)/H2O and (C12EO8 + 1% SDS)/H2O systems at 25°C, respectively.