Simultaneous X-ray diffraction and calorimetric study of metastable- to-stable solid phase transformation of 1,2-dipalmitoyl-sn-glycerol.
The thermal behaviour and structural changes associated with the phase transformation of 1,2-dipalmitoyl-sn-glycerol (DPG) were studied by means of simultaneous X-ray diffraction and differential scanning calorimetry. Metastable DPG solid phases are crystallized from the melted sample by thermal quenching. The metastable phase (alpha-phase) formed initially is converted into a stable phase (beta' phase) at approximately 50 degrees C on heating. It was found that the behaviour of the alpha- to beta'-phase transformation depends on the thermal history. DPG solid samples incubated at approximately 3 degrees C for more than 10 h after cooling transformed directly into the beta'-phase with heat release. On the other hand, in the solid samples without incubation, the alpha-phase once melted and then the crystallization of the beta'-phase occurred successively from the melted state.
D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D004075:Diglycerides / Q000737:chemistry*; D008968:Molecular Conformation; D013696:Temperature; D013816:Thermodynamics; D014961:X-Ray Diffraction