Abstract:

In constructing the phase diagram of glycerol monooleate (GMO)/EtOH/H2O mixts. the authors detected, in addn. to the well-characterized regions of lamellar and cubic bicontinuous liq. crystals, 3 addnl. 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 3rd 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 2 phase region connecting the 3 isotropic regions of the cubic, lamellar, and micellar phases. The authors termed this phase I2 (QL) phase or the QL phase, which stands for cubic liq. mesophase. This phase is a totally transparent and nonbirefringent fluid (completely pourable). It is stable even after over 9 mo of storage at room temp. 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 temp.-dependent measurements, and cryogenic-TEM (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. The authors expect that the fluidic ordered mesostructure will have future applications as a liq. vehicle for the solubilization of nutraceuticals, cosmetoceuticals, and pharmaceuticals. [on SciFinder(R)]