The structures of molecular aggregates in monooleoylglycerol-water systems were determined primarily by small angle X-ray diffraction method. Based on the results, the phase diagram in these systems were established. The structures of monoacylglycerol aggregates were found to change significantly with respect to time.
A reversed hexagonal phase (HII) was observed in the region of high monoacylglycerol concentration at higher temperature than Tc. The cubic phases (C1 and C2) were observed in the low concentration range. The cubic phase (C1) was found at 85 to 65 wt % monooloylglycerol, and the other cubic phase (C2) at less than 80 wt % monooloylglycerol. The cubic phases were transformed to the reversed hexagonal phase (HII) When the temperature exceeded 80°C.
The phase diagram obtained was essentially the same as that for monostearoylglycerol-water systems at higher temperature than Tc. Molecular rotation would thus appeal to occur in the region of high temperature and it follows that the two molecules should have the same geometry, that is a determining factor of liquid crystal structure.
The cubic phases (C1 and C2), each became the reversed hexagonal phase (H II) during several months of standing at room temperature.
