Dielectric Studies of Molecular Motions in Amorphous Solid and Ultraviscous Acetaminophen

Dielectric Relaxation and Crystallization of Ultraviscous Melt and Glassy States of Aspirin, Ibuprofen, Progesterone, and Quinidine

“…Here, we discuss our results in relevance to pharmaceuticals and neglect their implications for the controversial views on molecular motions in supercooled melts and on the currently debated theories of glass formation. A review of these aspects and their relation to the behavior of another pharmaceutical, acetaminophen, has been provided earlier, 42 which may be consulted.…”

“…Here, we report a dielectric relaxation spectroscopy study of molecular motions in the ultraviscous melt and the glassy states of four pharmaceuticals, aspirin, ibuprofen, progesterone, and quinidine, and compare their behavior against that of acetaminophen reported earlier. 42 Except for progesterone which lacks hydrogen bond donors, other pharmaceuticals contain both hydrogen bond donors and acceptors. Our main objective of these studies is to ultimately investigate the role of long-range and localized molecular diffusion as well as that of the distribution of the diffusion times on the rate of cold-crystallization and then finally relate the results to moleculespecific properties.…”

“…We have been experimentally studying the structural relaxation, 38 isothermal and nonisothermal ageing effects, 39 calorimetric relaxation time, 40 phase transformations, electrical conductivity, 41 and dielectric relaxation of pharmaceuticals 42,43 in their ultraviscous melt and glassy states. Here, we report a dielectric relaxation spectroscopy study of molecular motions in the ultraviscous melt and the glassy states of four pharmaceuticals, aspirin, ibuprofen, progesterone, and quinidine, and compare their behavior against that of acetaminophen reported earlier.…”

Crystallization Behavior of Acetaminophen in Nanopores

“…*Address correspondence to this author at the Universität Halle, Institut für Physik, FG Experimentelle Polymerphysik, Hoher Weg 8, D-06099 Halle/ Saale, Germany; Tel: +49 345 5525350; Fax: +49 345 5527351; E-mail: beiner@physik.uni-halle.de A suitable pharmaceutical model system to study the effects of confinement on the crystallization behavior is acetaminophen being a common analgesic and anti-pyretic drug existing in three different crystalline forms [13][14][15][16]. The chemical structure of this drug is shown in the insert of Fig.…”

“…The orthorhombic form II is metastable and melts at ~156°C [17,18]. Several preparation procedures have been reported to achieve these two crystalline forms either from solution or from the melt by thermal treatments [13][14][15][16]. A third polymorph of acetaminophen -called form III -is reported to be unstable and usually inaccessible in case of bulk samples.…”