Dresden 2009 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 1: Focus: Amphiphilic Systems I
CPP 1.6: Talk
Monday, March 23, 2009, 12:15–12:30, ZEU 222
Thermodiffusion of non-ionic sugar surfactants — •Bastian Arlt1, Sascha Datta2, Thomas Sottmann2, and Simone Wiegand1 — 1IFF - Weiche Materie, Forschungszentrum Jülich, Germany — 2Institut für Physikalische Chemie, Universität zu Köln, Germany
Thermodiffusion describes the formation of a concentration gradient due to a temperature gradient in a solution. The strength of this effect is described by the Soret coefficient (ST): a positive Soret coefficient of a component implies that this component moves to the cold side.
In this work we investigate the thermal diffusion behavior of non-ionic sugar surfactants in water using the IR-TDFRS [1] and the classical TDFRS [2]. First studies on C8G1 (n-Octyl β-D-glucopyranoside) indicate a pronounced change in ST at the critical micelle concentration (cmc) which coincides with an observation by Santos et al. [3], who observed a significant change in the strength of the thermal lens signal at the cmc. Furthermore, we observed a temperature dependent sign change in ST for higher concentrated solutions. With the classical TDFRS setup which uses a dye, we observe that ST is independent of the presence of dye, if the concentration is below the cmc, while ST differs for higher concentrations. We can conclude that the dye molecules are incorporated as a cosurfactant into the micelles.
[1] H. Ning et al., J. Phys. Chem. B, 112, 10927 (2008) [2] H. Ning et al., J. Phys. Chem. B, 110, 10746 (2006) [3] M. P. Santos et al., Phys. Rev. E 77, 011403 (2008)