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Published on: June 1, 2016
Systematic study of the thermal diffusion in associated mixtures.
Pavel Polyakov1, Simone Wiegand
1IFF-Weiche Materie, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany. p.polyakov@fz-juelich.de
The Journal of Chemical Physics
|January 22, 2008
Summary
This study investigates the Soret coefficient in various associated binary mixtures, revealing temperature-independent sign changes in some systems and temperature-dependent changes in others. Findings link thermal diffusion behavior to molecular interactions and structural fluid changes.
Area of Science:
- Physical Chemistry
- Thermodynamics
- Fluid Dynamics
Background:
- The Soret coefficient describes thermal diffusion in mixtures.
- Understanding thermal diffusion is crucial for various applications, including separation processes.
- Associated binary mixtures exhibit complex behavior due to intermolecular interactions.
Purpose of the Study:
- To systematically measure the Soret coefficient in diverse associated binary mixtures.
- To investigate the temperature and concentration dependence of the Soret coefficient.
- To correlate thermal diffusion behavior with molecular structure and interactions.
Main Methods:
- Utilized the thermal diffusion forced Rayleigh scattering (TDFRS) method.
- Performed systematic temperature and concentration-dependent measurements.
- Analyzed binary mixtures including water, deuterated water, DMSO, methanol, ethanol, acetone, 1-propanol, 2-propanol, and propionaldehyde.
Main Results:
- Identified mixtures with temperature-independent Soret coefficient sign changes (e.g., ethanol/water, acetone/water, DMSO/water).
- Observed temperature-dependent sign changes in other mixtures (e.g., 1-propanol/water, 2-propanol/water, ethanol/DMSO).
- Found a linear relationship between sign change concentration and vaporization enthalpies for specific systems.
Conclusions:
- The thermal diffusion behavior of associated mixtures is influenced by molecular structure and interactions.
- Hydrophilic and hydrophobic interactions, along with solubility, play a significant role in thermal diffusion.
- Results align with literature findings on structural changes observed via NMR, mass spectrometry, and X-ray experiments.
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