CQE - Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; IN - Institute of Nanoscience and Nanotechnology, Instituto Superior Tecnico, University of Lisbon, Avenida Rovisco Pais, 1049-001 Lisbon, Portugal.
CQE - Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal.
Int J Pharm. 2020 Jun 30;584:119410. doi: 10.1016/j.ijpharm.2020.119410. Epub 2020 May 21.
The thermal behavior of carvedilol and loratadine was studied by differential scanning calorimetry (DSC). The glass-forming ability, as well as the the tendency for crystallization from the glass (glass stability) and from the metastable and equilibrium melt were also investigated by DSC. In addition this technique was also used to characterize the glass transition of carvedilol and loratadine by determining the activation energy of the structural relaxation, the dynamic fragility, and the heat capacity jump associated with the glass transformation. Different aspects of the molecular mobility in carvedilol and loratadine were analyzed by Thermally Stimulated Depolarization Currents (TSDC), while in carvedilol the Dielectric Relaxation Spectroscopy (DRS) technique was also used. Carvedilol stands out for its high values of specific heat jump and dynamic fragility, which has been attributed to the particular mobility of this glass-former in the glass transformation region, a consequence of specific characteristics of its molecular structure. These molecular features are also at the origin of a relaxation above T that has been detected and characterized by TSDC; the DRS investigation allowed to better understand the molecular dynamics in carvedilol in the amorphous solid, in the metastable liquid state and in the glass transformation region. Finally, the secondary relaxations in loratadine were studied by TSDC, while those in carvedilol were studied by the two dielectric techniques and the results were compared and discussed.
采用差示扫描量热法（DSC）研究了卡维地洛和氯雷他定的热行为。还通过 DSC 研究了玻璃形成能力，以及从玻璃（玻璃稳定性）和亚稳和平衡熔体中结晶的趋势。此外，该技术还用于通过确定结构弛豫的活化能、与玻璃转变相关的动态脆性和热容跃变来表征卡维地洛和氯雷他定的玻璃转变。通过热刺激去极化电流（TSDC）分析了卡维地洛和氯雷他定中分子迁移的不同方面，而在卡维地洛中还使用了介电弛豫光谱（DRS）技术。卡维地洛的比热跃变和动态脆性值较高，这归因于其在玻璃转变区域内的特殊分子迁移率，这是其分子结构特定特征的结果。这些分子特征也是 TSDC 检测到和表征的 T 以上弛豫的起源；DRS 研究使我们能够更好地理解非晶固体、亚稳液态和玻璃转变区域中卡维地洛的分子动力学。最后，通过 TSDC 研究了氯雷他定的次级松弛，而通过两种介电技术研究了卡维地洛的次级松弛，并对结果进行了比较和讨论。
