PHASE-BEHAVIOR OF OCTYLDIMETHYL PARA-AMINO BENZOATE, POLYOXYETHYLENE-10-STEARYL ETHER, OLIVE OIL, AND WATER

The phase diagrams of octyl dimethyl para-amino benzoate (ODP)/polyoxy ethylene-10-stearyl ether (Steareth 10)/olive oil/water, and of ODP/po lyoxyethylene-4-lauryl ether (Laureth 4)/water systems were determined . ODP was solubilized in the lamellar liquid crystal of Steareth 10 wa ter and of Laureth 4 water to 15 and 12% by weight, respectively. Low- angle x-ray diffraction was used to determine the location of the ODP molecules in the liquid crystal. ODP penetrated between the hydrocarbo n chains of the surfactants, while olive oil was solubilized both at t hat site and between the terminal methyl group layers. The location of ODP in the liquid crystal was also reflected in ultraviolet absorptio n in the 260-350 nm region of the spectrum, which was compared to abso rption in a polar solvent, polyethylene glycol (260-340 nm), and in a nonpolar solvent, decane (260-328 nm).