Thermal and structural properties of sn‐1,3‐dipalmitoyl‐2‐oleoylglycerol and sn‐1,3‐dioleoyl‐2‐palmitoylglycerol binary mixtures examined with synchrotron radiation X‐ray diffraction

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, βC, 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. βC 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.