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@PHDTHESIS{Arlt:17829,
author = {Arlt, Bastian},
title = {{T}hermal diffusion in binary surfactant systems and
microemulsions; {J}uni 2011},
volume = {23},
school = {Universität Köln},
type = {Dr. (Univ.)},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {PreJuSER-17829},
isbn = {978-3-89336-819-8},
series = {Schriften des Forschungszentrums Jülich. Reihe Information
/ Information},
pages = {X, 159, XI-XLVI S.},
year = {2012},
note = {Record converted from JUWEL: 18.07.2013; Universität
Köln, Diss., 2011},
abstract = {In this work the thermal diffusion behavior of micellar
systems and microemulsions is studied. These model systems
are used to investigate two open questions. The first
question focuses on the influence of the micelle formation
around the critical micelle concentration ($\textit{cmc}$)
on the thermal diffusion behavior. In order to answer this,
we studied the thermal diffusion behavior of the nonionic
surfactant n–Octyl β–D–glucopyranoside
(C$_{8}$G$_{1}$) in water, which shows a fairly high
$\textit{cmc}$ at 0.65 wt\% for different concentrations
between w = 0.25 wt\% and w = 2.0 wt\% in a temperature
range from T = 15 $^{\circ}$C to 60 $^{\circ}$C using the
classical and infrared thermal diffusion forced Rayleigh
scattering ($\textit{TDFRS}$) setup. The $\textit{cmc}$ is
independently determined by surface tension measurements. In
classical TD-FRS experiments, the surfactant solutions show,
in the presence of a light-absorbing dye, a pronounced
change of the thermal diffusion coefficient, D$_{T}$, and
the Soret coefficient, S$_{T}$, at the $\textit{cmc}$. This
result agrees with a recent thermal lens study [Santos et
al., Phys.Rev. E 2008, 77, 011403 ], which showed, also in
the presence of dye, a pronounced change of the matter part
of the thermal lens signal around the $\textit{cmc}$. We
found that the change in the thermal diffusion properties
becomes less pronounced if the dye is absent or a light
source is used which is not absorbed by the dye. At higher
concentrations, we observed a temperature-dependent sign
inversion of S$_{T}$ as has also been found for solutions of
hard spheres at higher concentrations. We also studied the
sugar surfactants n–Heptyl β–D–glucopyranoside
(C$_{7}$G$_{1}$) and n–Octyl β–D–maltopyranoside
(C$_{8}$G$_{2}$), to investigate the influence of the number
of head groups and the length of the alkyl chain on the
thermal diffusion behavior. In the low concentration regime
around the $\textit{cmc}$, the abrupt change of S$_{T}$ was
confirmed for C$_{7}$G$_{1}$ and C$_{8}$G$_{2}$. Further,
the sign change in the high concentration regime was
confirmed. The second question is the radial dependence of
the Soret coefficient. It is controversially discussed
whether the radial dependence of S$_{T}$ is quadratic [...]},
cin = {ICS-3},
ddc = {500},
cid = {I:(DE-Juel1)ICS-3-20110106},
pnm = {BioSoft: Makromolekulare Systeme und biologische
Informationsverarbeitung},
pid = {G:(DE-Juel1)FUEK505},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/17829},
}