Using in-situ synchrotron radiation powder diffraction to characterize growth-related structural polymorphic phase transformations in cis-9-ω-octadecenoic acid

High resoln. synchrotron radiation powder diffraction was applied to examine structural polymorphism in high purity oleic acid (cis-9-ω-octadecenoic acid) after crystn. from the melt phase. X-ray data recorded from samples re-crystd. from the melt at ≈20° were consistent with a structure having 4 mols. to a monoclinic unit cell for both the α and γ polymorphs and lattice parameters of a 14.158, b 4.252, c 42.276 Å, β 96.211°, and a 14.986, b 5.267, c 44.271 Å, β 92.291°, resp. Data on the γ to α phase transformation was followed in-situ and revealed the formation of an intermediate quasi-amorphous interfacial structure prior to the phase transition with no obvious structural relation between the phases. Crystn. following pre-heating at ≈50° showed evidence for a different structure for the low temp. solidified compd. thus providing supporting evidence for the role of liq. phase structure on the resultant solid-state structure. [on SciFinder(R)]