Thermophoresis of cyclic oligosaccharides in polar solvents.
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 [Formula: see text]-, [Formula: see text]-, [Formula: see text]- and methyl-[Formula: see text]-cyclodextrin in water and formamide by infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS). In water the Soret coefficient, ST, of [Formula: see text]-, [Formula: see text]- and [Formula: see text]-cyclodextrin increases with increasing temperature and shows a sign change from negative to positive around T = 35°C, while STof methyl-[Formula: see text]-cyclodextrin is positive in the entire investigated temperature. In formamide ST-values of all cyclodextrins coincide and show a slight decrease with temperature. We discuss the obtained results and relate the ST-values to the different hydrogen bonding capabilities of the cyclodextrins and the used solvents. It turns out that the change of STwith temperature correlates with the partition coefficient, logP, which indicates that more hydrophilic substances show a more pronounced temperature sensitivity of ST. Additionally we obtained a surprising result measuring the refractive index contrast factor with temperature, [Formula: see text] of cyclodextrins in formamide, which might be explained by a complex formation between cyclodextrins and formamide.
School of Science, Tokai University, 259-1292, Kanagawa, Japan.
Kazuya
K
Eguchi
ICS-3 Soft Condensed Matter, Forschungszentrum Juelich GmbH, D-52428, Juelich, Germany.
Doreen
D
Niether
ICS-3 Soft Condensed Matter, Forschungszentrum Juelich GmbH, D-52428, Juelich, Germany.|Chemistry Department - Physical Chemistry, University Cologne, D-50939, Cologne, Germany.
Simone
S
Wiegand
School of Science, Tokai University, 259-1292, Kanagawa, Japan. rkita@keyaki.cc.u-tokai.ac.jp.|Micro/Nano Technology Center, Tokai University, 259-1292, Kanagawa, Japan. rkita@keyaki.cc.u-tokai.ac.jp.
Rio
R
Kita
D003102:Colloids / Q000737:chemistry; D003198:Computer Simulation; D003505:Cyclodextrins / Q000737:chemistry*; D004058:Diffusion; D005559:Formamides / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D009844:Oligosaccharides / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D055672:Static Electricity; D013696:Temperature; D014867:Water / Q000737:chemistry*
D003102:Colloids; D003505:Cyclodextrins; D005559:Formamides; D009844:Oligosaccharides; D012997:Solvents; D014867:Water; C031066:formamide
Topical Issue: Non-isothermal transport in complex fluids