Eur. Phys. J. E (2016) 39: 86
https://doi.org/10.1140/epje/i2016-16086-5

Regular Article

Thermophoresis of cyclic oligosaccharides in polar solvents

¹ School of Science, Tokai University, 259-1292, Kanagawa, Japan
² ICS-3 Soft Condensed Matter, Forschungszentrum Juelich GmbH, D-52428, Juelich, Germany
³ Chemistry Department - Physical Chemistry, University Cologne, D-50939, Cologne, Germany
⁴ Micro/Nano Technology Center, Tokai University, 259-1292, Kanagawa, Japan

^* e-mail: d.niether@fz-juelich.de
^** e-mail: rkita@keyaki.cc.u-tokai.ac.jp

Received: 21 July 2016
Accepted: 5 September 2016
Published online: 27 September 2016

Abstract

Cyclodextrins are cyclic oligosaccharides which are interesting as drug delivery systems, because they can be used as containers for pharmaceutical substances. We studied the Ludwig-Soret effect of -, -, - and methyl--cyclodextrin in water and formamide by infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS). In water the Soret coefficient, S _T, of -, - and -cyclodextrin increases with increasing temperature and shows a sign change from negative to positive around T = 35 ^° C, while S _T of methyl--cyclodextrin is positive in the entire investigated temperature. In formamide S _T-values of all cyclodextrins coincide and show a slight decrease with temperature. We discuss the obtained results and relate the S _T-values to the different hydrogen bonding capabilities of the cyclodextrins and the used solvents. It turns out that the change of S _T with temperature correlates with the partition coefficient, logP, which indicates that more hydrophilic substances show a more pronounced temperature sensitivity of S _T. Additionally we obtained a surprising result measuring the refractive index contrast factor with temperature, of cyclodextrins in formamide, which might be explained by a complex formation between cyclodextrins and formamide.