Liquid micellar discontinuous cubic mesophase from ternary monoolein/ethanol/water mixtures

In constructing the phase diagram of glycerol monooleate (GMO)/ethanol/water mixtures we detected, in addition to the well-characterized regions of lamellar and cubic bicontinuous liquid crystals, three additional isotropic transparent regions that were not previously well-defined: a large isotropic region denoted in early studies as the L-1-phase, an isotropic region with characteristics similar to the sponge L-3-phase, and a third isotropic region which had not been characterized previously. The present study deals with efforts to characterize this unique isotropic region. The isotropic region is an "island" located within a two phase region connecting the three isotropic regions of the cubic, lamellar, and micellar phases. We termed this phase I-2 (Q(L)) phase or the Q(L) phase, which stands for cubic liquid mesophase. This phase is a totally transparent and non-birefringent fluid (completely pourable). It is stable even after over 9 months of storage at room temperature. The fluid is of low viscosity and almost Newtonian. The new phase shows many characteristic features of an ordered phase. Small-angle X-ray scattering measurements (SAXS), SAXS-synchrotron temperature-dependent measurements, and cryogenic-transmission electron microscopy (cryo-TEM) observation reveal that the phase has a cubic symmetry. The SAXS diffractions indicate formation of a somewhat less ordered discontinuous cubic micellar mesophase. The cryo-TEM images provide strong evidence for ordered domains with cubic symmetry. Complementary measurements confirm that the phase is a unique case of a micellar cubic phase. We expect that the fluidic ordered mesostructure will have future applications as a liquid vehicle for the solubilization of nutraceuticals, cosmetoceuticals, and pharmaceuticals. (c) 2006 Elsevier B.V. All rights reserved.