The temperature-composition phase diagram and mesophase structure characterization of monopentadecenoin in water.

The temperature-composition phase diagram of monopentadecenoin, a monoacylglycerol with a cis monounsaturated fatty acid 15 carbon atoms long (C15:1c10) in water was constructed using x-ray diffraction. Low- and wide-angle diffraction patterns were collected from samples of fixed hydration as a function of temperature in the heating direction on x-ray-sensitive film. The temperature and hydration ranges investigated were 0-104 degrees C and 0-60% (w/w) water, respectively. The phases identified in the system include the lamellar crystalline phase, the lamellar liquid crystalline phase, the fluid isotropic phase, and two inverted cubic phases belonging to space groups la3d (Q230) and Pn3m (Q244). Particular attention has been devoted to the issues of phase equilibrium, phase boundary verification, and structure characterization. The phase diagrams of monopentadecenoin, monomyristolein (C14:1c9), and monoolein (C18:1c9) are compared, and the impact of molecular structure on mesophase stability and structure is discussed.