scholarly journals Glass-Transition Temperature of the β-Relaxation as the Major Predictive Parameter for Recrystallization of Neat Amorphous Drugs

2018 ◽  
Vol 122 (10) ◽  
pp. 2803-2808 ◽  
Author(s):  
Eric Ofosu Kissi ◽  
Holger Grohganz ◽  
Korbinian Löbmann ◽  
Michael T. Ruggiero ◽  
J. Axel Zeitler ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Amorphous Drugs ◽  
Β Relaxation

scholarly journals Pharmaceutical Amorphous Organic Materials Characterization by Using the Differential Scanning Calorimetry and Dynamic Mechanical Analysis

2011 ◽  
Vol 6 (2) ◽  
pp. 91-95
Author(s):  
Ion Dranca ◽  
Igor Povar ◽  
Tudor Lupascu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Dynamic Mechanical Analysis ◽  
Mechanical Analysis ◽  
Relaxation Processes ◽  
Scanning Calorimetry ◽  
Dynamic Mechanical ◽  
Β Relaxation

This research has been carried out in order to demonstrate the use of differential scanning calorimetry (DSC) in detecting and measuring α- and β-relaxation processes in amorphous pharmaceutical systems. DSC has been employed to study amorphous samples of poly (vinylpyrrolidone) (PVP), indomethacin (InM), and ursodeoxycholic acid (UDA) that are annealed at temperature (Ta) around 0.8 of their glass transition temperature (Tg). Dynamic mechanical analysis (DMA) is used to measure β- relaxation in PVP. Yet, the DSC has been used to study the glassy indomethacin aged at 0 and -10 oC for periods of time up to 109 and 210 days respectively. The results demonstrate the emergence of a small melting peak of the α-polymorph after aging for 69 days at 0°C and for 147 days at -10°C (i.e., ~55°C below the glass transition temperature) that provides evidence of nucleation occurring in the temperature region of the β-relaxation.

scholarly journals Correlation between High Temperature Deformation and β Relaxation in LaCe-Based Metallic Glass

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 833 ◽  
Author(s):  
Yinghong Chen ◽  
Jichao Qiao
Keyword(s):  
Glass Transition ◽  
High Temperature ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Strain Rate ◽  
Activation Volume ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Β Relaxation

High-temperature deformation around the glass transition temperature Tg and the dynamic mechanical behavior of La30Ce30Al15Co25 metallic glass were investigated. According to dynamic mechanical analysis (DMA) results, La30Ce30Al15Co25 metallic glass exhibits a pronounced slow β relaxation process. In parallel, strain-rate jump experiments around the glass transition temperature were performed in a wide range of strain rate ranges. The apparent viscosity shows a strong dependence on temperature and strain rate, which reflects the transition from non-Newtonian to Newtonian flow. At low strain or high temperature, a transition was observed from a non-Newtonian viscous flow to Newtonian viscous flow. It was found that the activation volume during plastic deformation of La30Ce30Al15Co25 metallic glass is higher than that of other metallic glasses. Higher values of activation volume in La30Ce30Al15Co25 metallic glass may be attributed to existence of a pronounced slow β relaxation. It is reasonable to conclude that slow β relaxation in La30Ce30Al15Co25 metallic glass corresponds to the “soft” regions (structural heterogeneities) in metallic glass.

β relaxation related to the glass transition temperature in polymeric gels

1999 ◽  
Vol 261 (3-4) ◽  
pp. 205-211 ◽  
Author(s):  
C Levelut ◽  
Y Scheyer ◽  
J Pelous ◽  
O Randl ◽  
F Prochazka ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polymeric Gels ◽  
Β Relaxation

Characterising glass transition temperatures and glass dynamics in mesoporous silica-based amorphous drugs

2019 ◽  
Vol 21 (35) ◽  
pp. 19686-19694 ◽  
Author(s):  
Eric Ofosu Kissi ◽  
Michael T. Ruggiero ◽  
Nele-Johanna Hempel ◽  
Zihui Song ◽  
Holger Grohganz ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Mesoporous Silica ◽  
Transition Temperatures ◽  
Glass Transition Temperatures ◽  
Drug Molecules ◽  
Glass Dynamics ◽  
Amorphous Drugs ◽  
Amorphous Drug

Amorphous drug molecules bound to MPS surface are restricted in mobility, but they exhibit a primary glass transition temperature.

Characterization of Glassy State Relaxations in Styrene and Methacrylate Based Nonlinear Optical Materials

1992 ◽  
Vol 247 ◽  
Author(s):  
Michael A. Schen ◽  
Fred I. Mopsik
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Nonlinear Optical ◽  
Glassy State ◽  
Polymer System ◽  
Mole Percent ◽  
Slow Relaxations ◽  
Β Relaxation ◽  
Dye Reorientation

ABSTRACTSub-Ts relaxations in polymethylmethacrylate (PMMA) and in narrow molecular weight polystyrene (PS) thin films with and without second order nonlinear optical dyes have been examined using time domain dielectric spectrometry. Dyes used include 4-[N, N-dimethylamino]-4’-nitrostilbene (DANS) and 4-[N-ethyl, N-hydroxyethylaminoJ-4’-nitroazobenzene (DR1) at a level of 0.19 mole percent. In dye/PS blends, dye relaxations are seen to occur at frequencies similar to the frequencies of the β-relaxation of pure PS below the glass transition temperature. Analysis of the glassy phase dispersion leads us to conclude that, at near room temperature, appreciable dye reorientation occurs on a time scale of a few seconds. This dye reorientation is coupled to the dynamic motions of the localized polystyrene subunits. Experiments using dye in PMMA did not conclusively reveal dye motions because of the intrinsically large dispersion of PMMA itself. The β-relaxation frequency range is higher in the PMMA dye/polymer blend than in dye-containing PS implying dye reorientation would likewise occur more rapidly than in PS. Our results indicate that the randomization of dye orientation observed in a dye/polymer system depends on the rapid, local chain motions which continue at temperatures well below the glass transition temperature, as well as on the long range, slow relaxations associated with the glass-to-rubber transition.

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