Thermal and Structural Properties on sn-1,3-Dipalmitoyl-2-oleoylglycerol and sn-1,3-Dioleoyl-2-palmitoylglycerol Binary Mixtures

Minato A., Ueno S., Yano J., Smith K., Seto H., Amemiya Y., Sato K., Thermal and Structural Properties on sn-1,3-Dipalmitoyl-2-oleoylglycerol and sn-1,3-Dioleoyl-2-palmitoylglycerol Binary Mixtures Examined with Synchrotron Radiation X-Ray Diffraction, Journal of the American Oil Chemists’ Society, 1997, 74 (10), 1213-1220

Thermodynamic and polymorphic behavior of POP (sn-1,3-dipalmitoyl-2-oleoylglycerol) and OPO (sn-1,3-dioleoyl-2-palmitoylglycerol) binary mixtures was examined using differential scanning calorimetry and conventional and synchrotron radiation X-ray diffraction. A molecular compound, β_C, was formed at the 1:1 (w/w) concentration ratio of POP and OPO, giving rise to two monotectic phases of POP/compound and compound/OPO in juxtaposition. β_C has a long-spacing value of 4.2 nm with a double chainlength structure and the melting point of 31.9°C. A structural model of the POP-OPO compound is proposed, involving the separation of palmitoyl and oleoyl chain leaflets in the double chainlength structure. In the polymorphic occurrence of the POP-OPO mixtures, the POP fraction transformed from α to β′ with no passage through γ, then transformed to β. The presence of OPO in POP promoted the β′–β transformation of POP during the melt-mediated crystallization.