Soret and mass diffusion measurements and molecular dynamics simulations of <i>n</i>-pentane–<i>n</i>-decane mixtures

Perronace, Andrea; Leppla, Cindy; Leroy, Frédéric; Rousseau, Bernard; Wiegand, Simone

doi:10.1063/1.1436473

Cited by 104 publications

(125 citation statements)

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“…Figure (8) shows that the reduced thermal diffusion factor defined by equation (16) fluctuates slightly with the carbon number of the n-alkane involved. Nevertheless, this figure indicates that * εσ α Tm deduced from computations is always close to the value given by equation (18), meaning that the way we defined the reduced thermal diffusion factor is consistent for such mixtures.…”

Section: Alkanes Equimolar Mixturesmentioning

confidence: 99%

“…Elsewhere, if such a relation in dense phases exists, this function should not be expressed in terms of the characteristic molecular parameters defined by equation (7)(8)(9)(10)(11) contrary to the others transport properties, because the amplitude of thermal diffusion depends on the discrepancy between the molecular parameters of the involved components and not on the characteristic parameters defined for example by (6), (7) and (9). This work provides a first step toward the establishment of such a function z for thermal diffusion.…”

Section: Models and Methods Usedmentioning

confidence: 99%

“…This is particularly true when dealing with experimentally inaccessible thermodynamics conditions or with weak phenomena such as thermal diffusion. In particular, molecular dynamics reveals itself to be a useful tool to improve our understanding of the physical processes that govern this transport phenomenon [2,[6][7][8][9] which is a compulsory step to build reliable correlations based on the law of the corresponding states [10] for simple mixtures.…”

Section: Introductionmentioning

confidence: 99%

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Thermal diffusion in Lennard–Jones fluids in the frame of the law of the corresponding states

Galliéro¹

2004

Fluid Phase Equilibria

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This work is related to the definition of a reduced thermal diffusion coefficient thanks to numerical microscale molecular dynamics simulations. This cross transport process, also called Soret effect, couples mass flux and thermal gradient and is still largely misunderstood. For this study, we have applied a boundary driven non equilibrium molecular dynamics algorithm on Lennard-Jones spheres mixtures. Simulations have been performed at a constant reduced supercritical state, using a van der Waals one fluid approximation in order to fulfil the law of the corresponding states. In binary mixtures, we have studied the molecular parameters and the molar fraction influences on thermal diffusion separately and then combined. It is shown that, on pressure and on thermal conductivity, the corresponding states law is fulfilled for a wide range of molecular 2 parameters ratios. In this frame, we have then constructed simple correlations which relate thermal diffusion factor to the mixture parameters. Combining the relations obtained, a reduced thermal diffusion factor taking into account all the various contributions has been defined. Finally, it is shown that this relation enables us to estimate thermal diffusion in various binary and ternary mixtures of Lennard-Jones spheres representing alkanes with a maximum deviation of 15 %.

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Section: Alkanes Equimolar Mixturesmentioning

confidence: 99%

Section: Models and Methods Usedmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermal diffusion in Lennard–Jones fluids in the frame of the law of the corresponding states

Galliéro¹

2004

Fluid Phase Equilibria

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“…The principle of the TDFRS method is described elsewhere in details 33 . An argon-ion laser (λ w =488 nm) is used for writing the temperature grating into the sample.…”

Section: Tdfrs Experiments and Data Analysismentioning

confidence: 99%

Systematic study of the thermal diffusion in associated mixtures

Polyakov

Wiegand

2008

The Journal of Chemical Physics

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We performed systematic temperature and concentration dependent measurements of the Soret coefficient in different associated binary mixtures of water, deuterated water, dimethyl sulfoxide (DMSO), methanol, ethanol, acetone, methanol, 1-propanol, 2-propanol, propionaldehyde using the so called thermal diffusion forced Rayleigh scattering method. For some of the associating binary mixtures such as ethanol/water, acetone/water and DMSO/water the concentration x ± w at which the Soret coefficient changes its sign does not depend on temperature and is equal to the concentration x × w where the Soret coefficient isotherms intersect. While for others such as 1-propanol/water, 2-propanol/water and ethanol/DMSO the sign change concentration is temperature dependent, which is the typical behavior observed for non-associating mixtures. For systems with x ± w = x × w we found that x ± w depends linearly on the ratio of the vaporization enthalpies of the pure components. Probably due to the similarity of methanol and DMSO we do not observe a sign change for this mixture. The obtained results are related to structural changes in the fluid observed by nuclear magnetic resonance, mass specrometric and X-ray experiments in the literature. Furthermore we discuss the influence of hydrophilic and hydrophobic interactions and the solubility on thermal diffusion behavior.

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“…31 The experimental details of thermal diffusion forced Rayleigh scattering (TDFRS) have been described elsewhere. 32 The normalized heterodyne signal intensity, het (t), to the thermal signal is related to the Soret coefficient S T and diffusion coefficient D as follows:…”

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confidence: 99%

Soret Coefficient of Poly(N-isopropylacrylamide)/Water in the Vicinity of Coil−Globule Transition Temperature

Kita

Wiegand

2005

Macromolecules

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According to thermodynamics of polymer solutions, polymers show conformational changes depending on the solvent quality. A transition of single polymer chain induced by the solvent quality change, known as a coilglobule transition, has been extensively studied because of their importance in not only polymer physics but also application aspects for the collapse of a gel network, the folding of a protein, and so on. [1][2][3][4][5][6] Poly(N-isopropylacrylamide) (PNiPAM) chain in water has a Θ temperature at 30.6°C, where the second virial coefficient is zero, and shows the coil-globule transition by heating. Indeed, there are many reports studying PNiPAM solutions by scattering methods, 7-10 fluorescence, 11 electronic paramagnetic resonance, 12 IR spectroscopy, 13,14 and calorimetry. 15,16 A considerable amount of work on PNiPAM solutions is collected in a review. 17 However, thermal diffusion phenomena, also called the Ludwig-Soret effect, have not been studied with taking into account the coil-globule transition in the vicinity of the Θ temperature.The Ludwig-Soret effect accounts for a mass flux, J 1 , in a mixture which is induced by a temperature and a concentration gradient. [18][19][20][21] Under a steady temperature gradient a steady concentration gradient is built up, where the flux vanishes (J 1 ) 0). The Soret coefficient, S T , is expressed as where D is the translational mass diffusion coefficient, D T the thermal diffusion coefficient, c 1 the mass fraction of component 1, and T the temperature.The sign of S T indicates whether component 1 migrates to the warm side or the cold side of the fluid. 22 If the system is dominated by short-range interactions, the thermal diffusion behavior can be attributed to single particle and collective contributions. 23 There are several detailed and systematic studies of thermal diffusion phenomena of organic polymer systems covering scaling behavior, concentration effects, and preferential solvation effects in mixed solvents. [24][25][26][27][28][29] In contrast to those organic systems, there are only few studies for aqueous polymer solutions.Observations of the Ludwig-Soret effect in the vicinity of coil-globule transition of PNiPAM/water will illuminate the importance of segment-segment and segment-solvent interactions. These key features can be varied experimentally according to the consequence of coil-globule transition of PNiPAM. This approach will lead to deeper understanding of thermal diffusion behavior of aqueous polymer systems as well as provide new insight into the solution properties of PNiPAM in a thermodynamically nonequilibrium state.PNiPAM was purified by a fractionation method. 8 One fraction was used in this study which had the weightaveraged molecular weight M w ) 3.0 × 10 6 g/mol with a polydispersity M w /M n of 1.20. Details of sample preparation and characterizations are described elsewhere. 30 Water was deionized by a Milli-Q system. In this study 1.0 g/L PNiPAM in water was prepared with a tiny amount of the dye, Basantol Yellow 215. 31 ...

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Soret and mass diffusion measurements and molecular dynamics simulations of n-pentane–n-decane mixtures

Cited by 104 publications

References 44 publications

Thermal diffusion in Lennard–Jones fluids in the frame of the law of the corresponding states

Thermal diffusion in Lennard–Jones fluids in the frame of the law of the corresponding states

Systematic study of the thermal diffusion in associated mixtures

Soret Coefficient of Poly(N-isopropylacrylamide)/Water in the Vicinity of Coil−Globule Transition Temperature

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