Crystallization kinetics of polymorphic forms of a molecular compound constructed by SOS (1,3-distearoyl-2-oleoyl- sn-glycerol) and SSO (1,2-distearoyl-3-oleoyl- rac-glycerol)

Abstract

Crystallization kinetics of binary mixture phases of SOS (1,3-distearoyl-2-oleoyl- sn-glycerol) and SSO (1,2-distearoyl-3-oleoyl- rac-glycerol) were examined with time-resolved X-ray diffraction (XRD) and DSC methods. Formation of three polymorphic forms, named α c, β′ c and β c, of a molecular compound was observed at a SOS/SSO=50/50 concentration ratio. The XRD data showed that all three polymorphs were arranged in a double chain-length structure, although a triple chain-length structure is formed in α and β′ forms of SSO, and β′ and β forms of SOS. The time-resolved XRD studies showed that α c and β c forms of the molecular compound crystallized more rapidly than the corresponding polymorphic forms of SOS and SSO. The results were discussed in terms of molecular chain–chain interactions of SOS and SSO, by assuming that kinetic processes of nucleation may prefer the formation of the α c and β c forms arranged in the double chain-length structure.