A SAXS-WAXS study of the endothermic transitions in amorphous or supercooled liquid itraconazole

Small and wide angle high energy x-ray scattering experiments were performed upon cooling itraconazole from the melt to investigate the structural origin of the two transitions at ∼74 °C and ∼90 °C observed in DSC measurements. Slight changes to the main WAXS peak at Q = 1.33 ± 0.01 Å⁻¹ were observed at 90 °C and are found to be inter-molecular in nature, suggesting a liquid to isotropic transition. This finding was supported by complementary wide angle neutron scattering measurements. For temperatures at and below ∼74 °C two strong rings appear in the 2D-SAXS pattern at Q = 0.24 ± 0.01 Å⁻¹ and 0.43 ± 0.01 Å⁻¹. The SAXS spectra were further deconvoluted into sharp and broad components. A narrowing of the broad component is associated with only minor changes in the packing arrangements of the itraconazole molecules below ∼90 °C, while the appearance of the sharp component below ∼74 °C is attributed to the formation of a polydomain lamellar phase.