Dresden 2009 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Focus: Amphiphilic Systems I

CPP 1.6: Vortrag

Montag, 23. März 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 (S_T): 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 S_T 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 S_T for higher concentrated solutions. With the classical TDFRS setup which uses a dye, we observe that S_T is independent of the presence of dye, if the concentration is below the cmc, while S_T 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)