Molecular motions in amorphous pharmaceuticals

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Dielectric Relaxation Spectroscopy (10(-1)Hz to 10(6)Hz) was used in order to get relevant information regarding the different modes of motion, from supercooled liquid down to the glassy state, present in the glass-forming Ibuprofen. This pharmaceutical drug easily avoids crystallization on cooling from the melt, forming a glass below the dielectric T(g)(100s)=226K, and undergoes cold crystallization upon further heating. In the supercooled state, attained from above, a dominating relaxation process associated with the glass transition was detected. The relaxation time temperature dependence of this a process presents the usual VFT type curvature found in non-pharmaceutical glass formers, which steepness gave a fragility index of m=93 allowing to classify ibuprofen as a fragile glass-former. In the glassy state, two secondary relaxation processes were found, beta and gamma, in decreasing temperature location. Analysis of the spectra using the Coupling Model confirms that the beta process is the genuine Johari-Goldstein relaxation probably playing a role in cold crystallization of ibuprofen.
Original languageUnknown
Title of host publicationAIP Conference Proceedings
EditorsM Tokuyama, I Oppenheim, H Nishiyama
Publication statusPublished - 1 Jan 2008
Event5th International Workshop on Complex Systems -
Duration: 1 Jan 2007 → …


Conference5th International Workshop on Complex Systems
Period1/01/07 → …

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