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 L1-phase, an isotropic region with characteristics similar to the sponge L3-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 I2 (QL) phase or the QL 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.