A structural study of the mesophases of two oxyethylene alkyl ether-decane-water systems, a comparison between technical grade C12EO〈7〉 and pure C12EO6

Abstract

As part of a study polyoxyethylene alkyl ethers (C m EO n ), water and decane, the phase diagram and the structures of the mesophases of pure C12EO6 and technical grade C12EO〈7〉 were compared. The constructed phase diagrams of the two systems show a great resemblance except for one difference: the viscous isotropic phase is only present in the C12EO6 phase diagram. The swelling behavior of the lamellar and hexagonal phases was studied with smallangle x-ray scattering. Both the lamellar and hexagonal phases showed an ideal swelling behavior and no differences between the lamellar and hexagonal phases of the two systems were detected. With freeze-fracture electron microscopy the hexagonal and lamellar phases were visualized. No differences in the textures of the lamellar phases were found, however, the micrographs of the hexagonal phases of the two systems clearly showed different textures. While in the hexagonal phase of the C12EO6 system only infinite long rods were visualized, short interrupted rods were found in the hexagonal phase of the C12EO〈7〉 system.