STABILIZATION OF A BICONTINUOUS CUBIC PHASE FROM POLYMERIZABLE MONOACYLGLYCEROL AND DIACYLGLYCEROL

Technological applications of lipids may be possible through stabiliza tion of various liquid-crystalline phases. One important approach to s tabilized self-assembling materials utilizes polymerization of liquid- crystalline phases composed of reactive lipids. Polymerization of lipi ds has been utilized to modify the chemical and physical properties of lamellar assemblies (e.g., lipid monolayers, multilayers, and bilayer vesicles). In addition, polymerization of the Lipid region of three-d imensional nonlamellar lipid-phase structures has recently been report ed, including the reversed bicontinuous cubic (Q(II)) phase, belonging to the space group Pn3m and the reversed hexagonal (H-II) phase. sere we show that sin easily prepared polymerizable monoacylglycerol combi ned in a 9/1 molar ratio with the corresponding polymerizable 1,2-diac ylglycerol forms nonlamellar phases upon hydration at room temperature . Phase investigation using cross-polarized light, H-2 NMR spectroscop y, and X-ray diffraction showed that the lipid mixture formed a well-d efined cubic phase from at least 5 to 45 degrees C. The X-ray diffract ion pattern corresponded to a cubic phase with 1a3d symmetry and a uni t cell size of 131 Angstrom at 25 degrees C. Polymerization to high co nversion of this cubic phase was accomplished via the thermal decompos ition of H2O2. The resultant polymers dissolved in organic solvent, in dicating they were not cross-linked. The visual clear character, cross -polarized light test, and X-ray diffraction showed that isotropic arc hitecture was maintained up to at least 70 degrees C after sample poly merization. The diffusion coefficient of water (23 degrees C) within t he polymerized cubic phase, determined by pulsed field gradient NMR sp ectroscopy, was 1.2 +/- 0.2 x 10(-10) m(2)/s, a value consistent with retention of the cubic phase during and after the polymerization. The biocompatible and mesoporous nature of the polymerized cubic phase sug gests it could be used as the host for incorporation of synthetic or b iological molecules in a manner that has already proven especially use ful in microporous solids.