Molecular Dynamics of Supercooled Pharmaceutical Agent Posaconazole Studied via Differential Scanning Calorimetry, Dielectric and Mechanical Spectroscopies.

Molecular Dynamics of Supercooled Pharmaceutical Agent Posaconazole Studied via Differential Scanning Calorimetry, Dielectric and Mechanical Spectroscopies.

Mol Pharm. 2013 Sep 9;

Authors: Adrjanowicz K, Kaminski K, Wlodarczyk P, Grzybowska K, Tarnacka M, Zakowiecki D, Garbacz G, Paluch M, Jurga S

Abstract
This paper presents comprehensive studies on the molecular dynamics of pharmaceutically important substance, posaconazole. In order to characterize relaxation dynamics in the supercooled liquid and glassy states of posaconazole dielectric and mechanical spectroscopies were applied. Dielectric data have indicated multiple relaxation process that appear above and below glass transition temperature Tg (tau_alpha=100s) of posaconazole. From the curvature of the dielectric versus inverse of temperature dependence we determine so-called 'fragility', being very popular parameter for classifying the structural dynamics of supercooled liquids and polymer. From the calculations we get m=150, means that it is one of the most fragile low molecular weight glass-forming liquids. In this paper, relaxation dynamics of supercooled posaconazole extracted from dielectric response function was also confronted with shear-mechanical relaxation. Finally, we present a direct comparison of the fragility and the number of dynamically correlated molecules Nc determined from dynamic calorimetry curves, dielectric and mechanical spectroscopies, showing a clear deviation in the picture of glass-transition dynamics generated by calorimetric and spectroscopic techniques.

PMID: 24010649 [PubMed - as supplied by publisher]