Journal
INTERNATIONAL JOURNAL OF PHARMACEUTICS
Volume 495, Issue 1, Pages 420-427Publisher
ELSEVIER
DOI: 10.1016/j.ijpharm.2015.09.012
Keywords
Amorphous; Biclotymol; Dipolar relaxation; Crystallization kinetics; Avrami law; Stability
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Funding
- Spanish Ministry of Science and Innovation [FIS2014-54734-P]
- Generalitat de Catalunya [2014 SGR-581]
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We employ dielectric spectroscopy to monitor the relaxation dynamics and crystallization kinetics of the Biclotymol antiseptic in its amorphous phase. The glass transition temperature of the material as determined by dielectric spectroscopy is T-g = 290 +/- 1 K. The primary (alpha) relaxation dynamics is observed to follow a Vogel-Fulcher-Tammann temperature dependence, with a kinetic fragility index m = 86 +/- 13, which classifies Biclotymol as a relatively fragile glass former. A secondary relaxation is also observed, corresponding to an intramolecular dynamic process of the non-rigid Biclotymol molecule. The crystallization kinetics, measured at four different temperatures above the glass transition temperature, follows an Avrami behavior with exponent virtually equal to n = 2, indicating one-dimensional crystallization into needle-like crystallites, as experimentally observed, with a time-constant nucleation rate. The activation barrier for crystallization is found to be E-a = 115 +/- 22 kJ mol (1). (C) 2015 Elsevier B.V. All rights reserved.
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