Collective relaxation dynamics and crystallization kinetics of the amorphous Biclotymol antiseptic
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 Tg=290±1K. The primary (a) relaxation dynamics is observ...
| Autores: | , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/81334 |
| Acceso en línea: | https://hdl.handle.net/2117/81334 https://dx.doi.org/10.1016/j.ijpharm.2015.09.012 |
| Access Level: | acceso abierto |
| Palabra clave: | Stability Amorphous semiconductors amorphous biclotymol dipolar relaxation crystallization kinetics avrami law stability kohlrausch-williams-watts domain havriliak-negami molecular mobility physical stability thermodynamic quantities secondary relaxations glass-transition state water time Semiconductors amorfs Àrees temàtiques de la UPC::Física |
| Sumario: | 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 Tg=290±1K. The primary (a) 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 Ea=115±22kJmol(-1) |
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