Temperature dependence of the diffusion, thermodiffusion and Soret coefficient of a dilute polystyrene/toluene solution as measured by means of a transient holographic grating technique

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Kantelhardt, Jannik ; Sommermann, Daniel ; Köhler, Werner:
Temperature dependence of the diffusion, thermodiffusion and Soret coefficient of a dilute polystyrene/toluene solution as measured by means of a transient holographic grating technique.
In: International Journal of Heat and Mass Transfer. Bd. 228 (2024) . - 125602.
ISSN 0017-9310
DOI der Verlagsversion: https://doi.org/10.1016/j.ijheatmasstransfer.2024.125602

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Abstract

We have measured diffusion, thermodiffusion and Soret coefficients of a dilute solution of polystyrene in toluene by means of the transient holographic grating technique of thermal diffusion forced Rayleigh scattering over a temperature range from 10 to 50 °C. The results show a systematic deviation from optical beam deflection measurements over a narrower temperature interval of the order of ten percent but the identical temperature dependence. A comparison with previous measurements from our laboratory, new control measurements and literature data does not lead to a clear conclusion about the correct values. From the diffusion coefficient a temperature independent hydrodynamic radius is obtained. Both the Soret coefficient and the viscosity-scaled thermodiffusion coefficient ηDT, for which a universal value has been reported in the case of asymmetric systems with large solute entities, decrease with temperature.