Collective relaxation dynamics and crystallization kinetics of the amorphous Biclotymol antiseptic
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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 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)
CitacióTripathi, P., Romanini, M., Tamarit, J. Ll., Macovez, R. Collective relaxation dynamics and crystallization kinetics of the amorphous Biclotymol antiseptic. "International journal of pharmaceutics", 10 Novembre 2015, vol. 495, núm. 1, p. 420-427.