Recherches Sur La Thermodiffusion En Phase Liquide

Prigogine, Ilya; Brouckère, Lucia De; Amand, Mme R.

doi:10.1016/0031-8914(50)90094-2

Cited by 74 publications

(35 citation statements)

References 5 publications

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“…However, in solutions with low water content, PEO is found to migrate to the warmer region of the fluid (S T < 0). Although changes in sign of the Soret coefficient have been reported for a number of liquid mixtures of small-molecule fluids, including alcohol solutions [12][13][14][15][16], the PEO/ethanol/water system appears to be the first polymer solution for which such a sign change has been observed.…”

Section: Introductionmentioning

confidence: 81%

Lattice Model for Thermodiffusion in Polymer Solutions

Luettmer-Strathmann

2005

Int J Thermophys

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Lattice Model for Thermodiffusion in Polymer Solutions 1 J. Luettmer-Strathmann 2When a temperature gradient is applied to a polymer solution, the polymer typically migrates to the colder regions of the fluid as a result of thermal diffusion (Soret effect). However, in recent thermodiffusion experiments on poly(ethylene-oxide) (PEO) in a mixed ethanol/water solvent it is observed that for some solvent compositions the polymer migrates to the cold side, while for other compositions it migrates to the warm side. In order to understand this behavior, a two-chamber lattice model for thermodiffusion in liquid mixtures and dilute polymer solutions has been developed. For mixtures of PEO, ethanol, and water, the compressibility and hydrogen bonding between PEO and water molecules are taken into account and Soret coefficients are calculated for a given temperature, pressure, and solvent composition. The sign of the Soret coefficient of PEO is found to change from negative (polymer enriched in warmer region) to positive (polymer enriched in cooler region) as the water content of the solution is increased, in agreement with experimental data. A close relationship between the solvent quality and the partitioning of the polymer between the two chambers is noted, which may explain why negative Soret coefficients for polymers are so rarely observed. The Soret effect in ethanol/water mixtures is also investigated and a change in sign of the Soret coefficient of water is found at high water concentrations, in qualitative agreement with experimental data.

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Section: Introductionmentioning

confidence: 81%

Lattice Model for Thermodiffusion in Polymer Solutions

Luettmer-Strathmann

2005

Int J Thermophys

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“…6,11,12 For many associating liquids, where specific interactions such as hydrogen-bonding or electrostatic interactions exist, sign changes of S T with composition have been observed. 6,9,15,16 Molecular dynamics (MD) simulations have become an important tool in the investigation of thermal diffusion behavior of Lennard-Jones model fluids and small-molecule liquids. [17][18][19][20][21] Lately, the simulation techniques for non-equilibrium properties have been improved, which have led to a reasonable agreement between simulations and experiments for associating and non-associating liquid mixtures.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of the Soret effect in acetone/water and dimethylsulfoxide/water mixtures

Ning

Wiegand²

2006

The Journal of Chemical Physics

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“…15,16 In contrast, sign changes in alcoholic mixtures without water require the consideration of entropic effects. 17 Presently, there is no microscopic understanding of the sign change in the thermal diffusion behavior. Often sign changes occur when the solvent quality becomes poorer, but this explanation can be ruled out because the second virial coefficient remains constant in the investigated temperature range.…”

Section: B Thermal Diffusion Of Pnipammentioning

confidence: 99%

“…15,16 Nevertheless, this argument is not always sufficient to explain a sign change in all mixtures. Prigogine, Debrouckere, and Amand, 17 argued that for alcoholic mixture, e.g., ethanol/cyclohexane, a free energy argument is needed which accounts for the loss in entropy.…”

Section: Introductionmentioning

confidence: 99%

Thermally induced sign change of Soret coefficient for dilute and semidilute solutions of poly(N-isopropylacrylamide) in ethanol

Kita

Kircher

Wiegand

2004

The Journal of Chemical Physics

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We studied the thermal diffusion behavior of poly(N-isopropylacrylamide͒ ͑PNiPAM͒ in ethanol in a temperature range from Tϭ14.0°C to Tϭ40.0°C by means of thermal diffusion forced Rayleigh scattering. The obtained Soret coefficient S T of PNiPAM was positive for lower temperatures (TϽ34°C), while S T showed a negative value for higher temperatures (TϾ34°C). This means PNiPAM molecules move to the cold side for temperatures TϽ34°C, whereas they move to the warm side for TϾ34°C. This is the first nonaqueous polymeric system for which a sign change with temperature has been observed. We performed static and dynamic light scattering experiments in the same temperature range. The second virial coefficient determined from dilute solutions by static light scattering ͑SLS͒ was positive in the comparable temperature range. The results of SLS for the semidilute solution showed a strong repulsion among PNiPAM chains which was enhanced by increasing temperature. These results imply that the observed thermally induced sign change of S T does not depend on the intermolecular interactions among PNiPAM chains.

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Recherches Sur La Thermodiffusion En Phase Liquide

Cited by 74 publications

References 5 publications

Lattice Model for Thermodiffusion in Polymer Solutions

Lattice Model for Thermodiffusion in Polymer Solutions

Experimental investigation of the Soret effect in acetone/water and dimethylsulfoxide/water mixtures

Thermally induced sign change of Soret coefficient for dilute and semidilute solutions of poly(N-isopropylacrylamide) in ethanol

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