The Soret effect of mono-, di- and tri-glycols in ethanol

Abstract

We employed thermal diffusion forced Rayleigh scattering (TDFRS) to investigate the chain length dependence of the thermal diffusion behavior of short glycols in ethanol. We studied three glycols, monoethylenglycol (MEG), diethylenglycol (DEG) and triethylenglycol (TEG), in an ethanol solution. In contrast to the polymer polyethylenglycol, the shorter glycols used within the framework of this study are completely soluble in ethanol, at least for low molar fractions. In order to guarantee a good solubility of the glycols, the measurements were limited to molar fractions of 10% and 20%. As the different glycols only differ by their chain length it will be possible to deduce its influence on the thermal diffusion properties. Due to the fairly short persistence length of the glycols, D_T reaches already for the dimer a plateau value. This finding agrees with simulation results. Furthermore, the thermal expansion and the kinematic viscosity are measured to investigate if empirical correlations seen for other systems could be confirmed.