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

Abstract

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 o C and ~90 o C observed in DSC measurements. Slight changes to the main WAXS peak at Q=1.33±0.01 Å -1 were observed at 90 o C and are found to be inter-molecular in nature, suggesting an isotropic liquid to isotropic transition. This finding was supported by complementary wide angle neutron scattering measurements. For temperatures at and below ~74 o 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 o C, while the appearance of the sharp component below ~74 o C is attributed to the formation of a polydomain lamellar phase. INTRODUCTION.

Organic Glasses with Tunable Liquid-Crystalline Order

“…This latter result indicates that above 330 K, our measurement obtains the equilibrium smectic order, since the same order is observed during cooling and reheating. This conclusion is further supported by the result of Benmore et al [16] who performed similar measurements on ITZ, but without a reheating step, using a larger capillary tube (2 mm in diameter) and slower cooling rate (2 mK/s). They found a similar increase of smectic order with cooling; our fitting of their data to a power law yields x = 0.68 and T Sm/N = 349 K, in excellent agreement with our values.…”

“…The process of smectic ordering was confirmed by X-ray scattering (Fig. 1b) [14,16]. ITZ was placed in a capillary tube (0.7 mm diameter) and measured in the transmission mode (Bruker SMART APEX2 diffractometer with a Cu Kα source) [17,18].…”

Vapor deposition of a nonmesogen prepares highly structured organic glasses

“…In contrast to the liquidcooled glass, the vapor-deposited glass has a high level of translational smectic-like order, which produces the intense peaks at q z values of ∼(0.2, 0.4, and 0.6) Å −1 . These 3 peaks resemble those of the equilibrium smectic liquid-crystal phase of itraconazole (28,29), suggesting that the order in the vapordeposited glass of posaconazole is smectic-like. Corrected for instrumental broadening, the Scherrer correlation length of the peak at q z ∼ 0.4 Å −1 is 18.4 nm, which is equal to approximately 6 molecular lengths.…”

Vapor-Deposited Glass Structure Determined by Deposition Rate–Substrate Temperature Superposition Principle

“…In this work, we utilize a wide range of deposition rates and substrate temperatures to prepare glasses of itraconazole, a glass-forming smectic liquid crystal. We characterize the molecular orientation of the glasses by spectroscopic ellipsometry and the anisotropic layering by grazing-incidence wide-angle X-ray scattering (GIWAXS). , Itraconazole is an ideal choice for these experiments as its liquid and liquid-cooled glass have been well-characterized. − Previous vapor deposition experiments have established that depositing at different substrate temperatures can prepare glasses of itraconazole with a wide range of molecular orientations, with some deposition conditions preparing glasses with high levels of smectic order. These features provide a rich set of observables for investigating the influence of deposition rate on glassy molecular packing.…”

“…Integrations along the azimuthal direction over an 80° range of angles are shown in Figure c. We quantify the peak position, as it is an unambiguous measure of spacing between smectic layers . For the sample deposited at 335 K, the second-order peak occurs at smaller q , indicating increased spacing between smectic layers.…”