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Recent experiments for various amides and sugars showed a clear correlation of the temperature dependence of the Soret coefficient with the hydrophilicity, quantitatively described by the logarithm of the 1-octanol/water partition coefficient $\log P$. This coefficient is a measure for the hydrophilicity/hydrophobicity balance of a solute and is often used to model the transport of a compound in the environment or to screen for potential pharmaceutical compounds. In order to validate whether this concept works also for other water soluble molecules we investigated systematically the thermophoresis of mono- and poly hydric alcohols. As experimental method we use a holographic grating technique called infrared Thermal Diffusion Forced Rayleigh Scattering (IR-TDFRS). Experiments showed that the temperature dependence of the Soret coefficient of polyhydric alcohols also correlates with $\log P$ and lies on the same master plot as amides and sugars.

We measured the binary diffusion coefficient and the Soret coefficient in the fabrication system of organic photovoltaics (OPVs) by the holographic grating technique we call Soret forced Rayleigh scattering (SFRS). To test the validity of the apparatus we built, we here performed measurements on binary benchmark mixtures: three types of binary solutions (50 wt %) composed of n-dodecane, isobutylbenzene, and 1,2,3,4-tetrahydronaphthalene, at 298.2 K. Our experimental results for the diffusion coefficient and the Soret coefficient agree with the benchmark values within ± 10 %. The uncertainties estimated based on the Guide to the Expression of Uncertainty in Measurement (GUM) for the Soret coefficient on the benchmark mixtures are within 16 % with the coverage factor of k = 2. For OPV systems, our measurements were performed on [60]fullerene or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) solved in o-dichlorobenzene. We evaluated the Soret coefficient and the diffusion coefficient across a wide concent...

A detailed review of the experimental investigations of the thermodiffusion/thermophoresis process in liquid and gaseous mixtures is presented. Experiments in the laboratories on earth as well as studies in a microgravity environment in space have been described. The former include the non-optical apparatus such as the classical Soret cell , thermodiffusion column , two-chamber thermodiffusion cell and the thermal field-flow fractionation , as well as the optical techniques, viz., classical Soret cell with beam deflection, thermal diffusion forced Rayleigh scattering, thermal lens method and the microfluidic fluorescence method. These methods are discussed along with their advantages and disadvantages. Experiments performed in the microgravity environment are also discussed.

In the present work we studied the thermal diffusion behavior of n-decane in various alkanes by thermogravitational column (TC) technique and the thermal diffusion forced Rayleigh scattering (TDFRS) method. The investigated lighter alkanes compared to n-decane are n-pentane, n-hexane, n-heptane, n-octane, and the heavier ones are n-tetradecane, n-pentadecane, n-hexadecane, n-heptadecane, n-octadecane, and n-eicosane. The binary mixture n-decane/ n-pentane we investigated at several different concentrations; all other mixtures were only investigated at a mass fraction of 50%. Even for the volatile n-pentane/ n-decane mixture the deviations between the thermal diffusion coefficients determined by the different methods agreed within the error bars. Typically the agreement between the two methods was in the order of 5%. In comparison to recently published TC and TDFRS data we found deviations in the order of 30% up to 40%. We analyze and discuss the possible reasons for the discrepancies for the present and the past publications.

The Soret forced Rayleigh scattering method (S-FRSM) for measurement of mass diffusion coefficient has been developed. In the present paper, the theoretical analysis of the systematic effects of the experimental setup is discussed. It includes the analysis of : (1) effect of dye, (2) effect of sample thickness, (3) effect of Gaussian beam intensity distribution and (4) effect of heating duration time. The analysis of three-dimensional diffusion equation which takes into account the practical experimental conditions has clarified the influence quantity of the inadequate experimental settings. According to the present analysis, it has been found that the difference of diffusion coefficient can be negligible by employing the appropriate setting of experimental parameters. As a result of these considerations, the reliable optimization method of the measuring conditions in S-FRSM can be provided.

The diffusion of coil-rod-coil triblock copolymers in entangled coil homopolymers is experimentally measured and demonstrated to be significantly slower than rod or coil homopolymers of the same molecular weight. A model coil-rod-coil triblock was prepared by expressing rodlike alanine-rich α-helical polypeptides in E. coli and conjugating coillike poly(ethylene oxide) (PEO) to both ends to form coil-rod-coil triblock copolymers. Tracer diffusion through entangled PEO homopolymer melts was measured using forced Rayleigh scattering at various rod lengths, coil molecular weights, and coil homopolymer concentrations. For rod lengths, L, that are close to the entanglementh length, a, the ratio between triblock diffusivity and coil homopolymer diffusivity decreases monotonically and is only a function of L/a, in quantitative agreement with previous simulation results. For large rod lengths, diffusion follows an arm retraction scaling, which is also consistent with previous theoretical predictions. These experimental results support the key predictions of theory and simulation, suggesting that the mismatch in curvature between rod and coil entanglement tubes leads to the observed diffusional slowing.

We propose a new method for analysis of nonmonotonic forced Rayleigh scattering (FRS) decay profiles. It is shown that the curvature near the local maximum of a decay–grow–decay profile or a grow–decay profile can be used to determine directly the geometric mean of the unperturbed and photoproduct diffusion coefficients, which will in many cases mitigate the need to apply multiparameter nonlinear fitting routines. FRS tracer‐diffusion measurements of methyl red in poly(vinyl acetate)/toluene solutions at two different probe wavelengths, analyzed using the new method, are in good agreement with results of previous studies. Simulations are used to estimate the systematic error due to the approximation employed, and it is concluded that accuracies of a few percent or better should be routinely achievable in most cases. We have, in addition, investigated the probe‐wavelength dependence of the profile shape for this system.

We investigated the chain length dependence of the thermodiffusion behavior of oligosaccharides by the infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS) technique. Three disaccharides, sucrose, cellobiose and maltose, two trisaccharides, melezitose and raffinose, and a tetrasaccharide, stachyose, have been studied. We determined the thermal diffusion (D(T)), mass diffusion (D), and Soret (S(T)) coefficient as a function of temperature and concentration. While monosaccharides in water accumulate at the cold side in the investigated temperature (20-50 degrees C) and concentration (0.2-0.6667 wt) range, oligosaccharides enrich on the warm side with decreasing temperature or increasing sugar concentration. Additionally, we determined the kinematic viscosity (nu), the density (rho), and the thermal expansion coefficient (alpha) of the mixtures in order to check the linear correlation between D(T) and the ratio alpha/nu, which has been recently found for aqueous solutions of monosaccharides and for alkane mixtures. Finally, we found that D(T) and D decay with increasing chain length of the oligosaccharides in the whole studied range of temperatures, in contradiction with experimental results for nonpolar mixtures and theoretical predictions.

We have developed a new apparatus to measure the thermal diffusivity of liquids by the forced Rayleigh scattering method using a CO2 laser. In the case of employing the infrared wavelength laser as a heating source, it is less necessary to add dye substances in samples than with the previously used Ar+ laser. The purpose of the present study is to develop a practical forced Rayleigh scattering apparatus applicable to a wide range of substances and conditions. In the present study, we have invented a free-surface-heating technique which does not require any cell windows. In order to demonstrate the applicability of the present apparatus without adding dye substances, we have preliminarily measured the thermal diffusivity of molten KNO3 and a molten carbonate mixture (Li2CO3-Na2CO3-K2CO3=43.5-31.5-25.0mol%) in the temperature range up to about 1000K.

強制レイリー散乱法の原理、 誤差要因の検討、 最適測定条件の設定法等を示し、 測定装置の概説および本測定方法で初めて可能になった、 液晶の温度伝導率異方性と高温溶融塩の測定結果をまとめた。

The paper reports measurements of the thermal diffusivity of four molten alkali chlorides (LiCl, NaCl, RbCl and CsCl) in the temperature range above 1000°C by the forced Rayleigh scattering method. The dye substance employed is K2Cr2O7 in order to color the transparent molten salts. The accuracy is estimated to be ±4 to ±11% depending on the measured substances. In comparison with the present results converted to thermal conductivity, most of the previous experimental data obtained by steady-state methods show larger values (up to about five times) which may be due to the presence of convection and radiation. It is found that the thermal conductivity of these series of molten alkali metal chlorides decreases with increasing molecular weight, and the temperature coeffcients are weakly negative.

Forced Rayleigh Scattering (FRS) is a powerful technique for investigating heat and mass transfers in colloids. In the present work, we determine the Soret coefficient ST and the thermal diffusion coefficient DT of magnetic colloids (ferrofluids). It has been theoretically predicted that the thermal diffusion coefficient DT of colloids depends both on the particle/solvent interfacial interaction and on the interactions between the colloidal particles. In order to understand the microscopic behavior of the Soret effect in these ionic magnetic colloids, experiments are performed on aqueous samples of various volume fractions Φ and ionic strengths. The dominant effect on the Soret coefficient comes here from the particle/solvent interaction and determines its sign. Interparticle interactions have an influence on ST in the moderate concentration range where virial like expansions are possible. In this range (Φ ≤ 0.10) and within the experimental error bar, the thermal diffusion does not depend on the ionic strength of the dispersion and the Φ-dependence of the friction coefficient is comparable to that of hard spheres. At larger concentrations, the thermal diffusion drastically decreases as the colloid approaches its dynamical glass transition. KEYWORD: Ferrofluids, Forced Rayleigh Scattering, thermal diffusion, Soret effect, friction, dynamical arrest.

The thermal diffusion behavior of acetone/water and dimethylsulfoxide(DMSO)/water mixtures has been experimentally investigated by a transient holographic grating technique named thermal diffusion forced Rayleigh scattering (TDFRS). For both systems a sign change of the Soret coefficient S(T) with varying water content has been predicted by simulations [C. Nieto Draghi et al., J. Chem. Phys. 122, 114503 (2005)]. The sign change of S(T) is confirmed by the experiment. Except for equimolar concentrations of acetone/water the agreement between the experimental and simulation data is reasonable.

Magnetic colloidal suspensions are used in numerous practical applications. However, their structural and dynamical properties are hardly known, particularly under an external applied field. For this purpose, an approachthat couples Brownian dynamics numerical simulations together with experimental measurements on tailored aqueous dispersions has been carried out. The use of scattering techniques, especially neutron scattering, enabled us not only to decipher the local structure but also to examine the translational dynamics at several length-scales. The effect of an external magnetic field has been measured and calculated parallely by the numerical simulation. Moreover, the rotational dynamics has been probed by magneto-optical birefringence relaxation measurements. The comparison between experimental and numerical results has improved the knowledge of the system, emphasising the role of the dipolar interaction., Les suspensions colloïdales magnétiques sont utilisées dans de nombreuses applications pratiques. Toutefois, leurs propriétés structurales et dynamiques, en particulier en présence d'un champ appliqué, restent mal connues. Dans ce but, nous avons adopté une approche qui couple une modélisation par simulation numérique de dynamique brownienne à plusieurs techniques expérimentales sur des dispersions aqueuses préparées «sur mesure». L'emploi de la diffusion de rayonnement, en particulier de neutrons, a permis d'une part, l'élucidation de la structure locale et d'autre part, l'examen de la dynamique de translation à plusieurs échelles. L'effet d'un champ extérieur a été mesuré et évalué parallèlement par la simulation numérique. De plus, la dynamique de rotation a été sondée par la relaxation de biréfringence magnéto-optique. La confrontation des résultats expérimentaux et de simulation numérique complète la compréhension du système, soulignant le rôle des interactions dipolaires.

Thermal diffusion forced Rayleigh scattering results on thermal diffusion of poly(ethylene oxide) (PEO) in ethanol/water mixtures are presented. In water-rich solvent mixtures, PEO is found to migrate towards regions of lower temperature. This is typical for polymer solutions and corresponds to a positive Soret coefficient of PEO. In solvent mixtures with low water content, however, the polymer is found to migrate towards higher temperatures, corresponding to a negative Soret coefficient of PEO in ethanol-rich solutions. To our knowledge, this is the first observed sign change of the Soret coefficient of a polymer in solution. We also present a simple lattice model for the polymer solvent system and calculate Soret coefficients with statistical mechanics methods. The calculated values agree qualitatively with the experimental results.

An analytical formula for the ratio between the long- and short-time self-diffusion coefficient ${\mathit{D}}_{\mathit{L}}$/${\mathit{D}}_{\mathit{S}}$ is presented as a result of extensive Brownian dynamics simulations for Yukawa systems. In addition, forced Rayleigh scattering experiments are performed to determine ${\mathit{D}}_{\mathit{L}}$/${\mathit{D}}_{\mathit{S}}$ for suspensions of highly charged latex spheres with a variable low volume fraction immersed in electrolytes of variable concentration. Experimental parameters were precisely controlled using advanced preparational methods. Comparing experimental data to the analytical formula we perform a sensitive dynamical test of Yukawa models for the interaction potential. The observed quantitative agreement provides strong evidence for the validity of the renormalization procedures suggested within the Poisson-Boltzmann cell model [J. Chem. Phys. 80, 5776 (1984)]. Deviations observed for the Dejarguin-Landau-Verwey-Overbeek potential and other models are discussed.

In this work, forced Rayleigh scattering is combined with a new deionization technique to measure the self-diffusion coefficient of strongly interacting charged polystyrene particles. For each measurement the, actually continuous, deionization process is stopped, allowing the suspension to relax from a sheared state to an equilibrium state. Conductivity and diffusion coefficient are monitored, both during this relaxation to equilibrium, and in dependence of the total deionization time. Relaxational behavior in the diffusion coefficient is observed in samples of both fluid and crystalline equilibrium state, while the conductivity remains unchanged. With increasing total deionization time the conductivity reaches a minimum and rises again to a stable plateau. The self-diffusion coefficient in equilibrium (i.e., at rest) also drops with increasing deianization time for monodisperse samples to unmeasurably low values, On the other hand, a finite, but small diffusion coefficient is found for the charge bidisperse sample.

The hydrodynamic relaxation rate for water inhomogeneities in aligned lipid-water smectics is measured for the first time using an improved version of the "forced Rayleigh" technique. Variation of the relaxation rate with water concentration yields a distinction between "bound" and "free" water.

In the present paper we describe the theoretical analysis of error factors of the forced Rayleigh scattering method to measure the thermal diffusivity of liquids. The error factors we considered here are ; 1) effect of sample wall, 2) effect of dye, 3) effect of Gaussian beam intensity distribution, 4) effect of heating duration time, all of which hinder the one-dimensional heat conduction assumed in the basic theory. The entire analysis is divided into two parts ; namely weak absorption analysis and strong absorption analysis. This is because the individual error factors cannot be superimposed in the case of a high dye concentration. According to the present study it is concluded that the experimental conditions can be so chosen that the amount of total error is negligible.

A new apparatus to measure the thermal diffusivity of liquids based on the forced Rayleigh scattering method was developed. Verification of the theory and examination of error factors have been carried out through measurement of the thermal diffusivity of toluene and water. The error factors examined in the present study were; sample layer thickness, concentration of dye and heating pulse duration time. Through these considerations, appropriate experimental conditions for the measurement were determined. To demonstrate the applicability of this method, the thermal diffusivities of toluene, n-hexane and methanol have been measured at room temperature. The accuracy of the present measurement was estimated to be±3 %. The present study may lead to the conclusion that the forced Rayleigh scattering method has considerable potential of being applied to measurements for electrically conducting liquids at high temperature.

Self Diffusion of Polymers in the Concentrated Regime I. Temperature Dependence of the Self Diffusion Coefficient and the Steady Viscosity of Polystyrene in Dibutyl Phthalate

We report on preliminary forced Rayleigh scattering experiments in a microemulsion system close to a critical point. It is shown for the first time that electrostriction induces sizable concentration gradients in a critical liquid mixture. The amplitude and the relaxation time of the induced gratings are found to increase divergently in the vicinity of the critical point, as expected from the known critical behaviors of the osmotic compressibility and of the correlation length of the concentration fluctuations.

Poursuivant la réalisation de méthodes de caractérisation d'un fluide en écoulement par diffusion Rayleigh forcée, nous avons mis au point une technique de marquage d'une figure bidimensionnelle quelconque dans le fluide par imagerie optique. L'impression de ce réseau et la visualisation directe de sa déformation permettent d'obtenir une mesure directe des composantes du gradient de vitesse.

Nonlinear optics is a powerful tool to investigate interfaces. We work in the Kretschmann configuration to carry out new experiments in the picoseconds regime. Phase conjugation is observed in two different configurations: one in which all the waves are surface plasmons and the other in which the pumps are plasmons while the probe is a volume wave. Here, the dominant nonlinearity is of thermal origin. In a similar experiment, we carry out the coupling of a volume wave into the corresponding surface Plasmon by means of a transient surface relief grating. That permits to highlight the excitation of different modes of surface acoustic waves., L'optique non linéaire est un puissant moyen d'investigation des interfaces. Nous nous plaçons dans la configuration de Kretschmann pour réaliser de nouvelles expériences en régime picoseconde.On décrit l'observation de conjugaison de phase dans deux configurations différentes: l'une dans laquelle toutes les ondes sont des plasmons de surface et l'autre dans laquelle les pompes sont des plasmons tandis que la sonde est une onde de volume. Ici, l'essentiel des processus non linéaires est d'origine thermique.Dans une expérience analogue, nous réalisons le couplage d'une onde de volume au plasmon de surface correspondant par l'intermédiaire d'un réseau induit. A cette occasion, nous mettons en évidence l'excitation d'ondes acoustiques de surface.