Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: POSTERS Colloids and Liquids

CPP 39.11: Poster

Thursday, March 26, 2009, 17:00–19:30, P3

Critical Casimir Forces in Colloidal Suspensions on Chemically Patterned Surfaces — •Olga Zvyagolskaya, Florian Soyka, Dominik Vogt, Christopher Hertlein, Laurent Helden, and Clemens Bechinger — Universität Stuttgart, 2. Physikalisches Institut, Pfaffenwaldring 57, 70569 Stuttgart

We investigate the behavior of colloidal particles immersed in a binary liquid mixture of water and 2,6-lutidine in the presence of a chemically patterned substrate. Close to the critical point of the mixture, the particles are subjected to critical Casimir interactions with the force acting between the surfaces of the particles as well as between the particle and the wall. The strength and sign of these interactions depend on the surface properties and the mixture's temperature. Between equally coated surfaces an attractive force arise, a repulsive force occurs between contrarily coated surfaces. Chemically patterned substrates are created by first coating the substrate with a layer of one adsoption preference which is then locally removed creating a pattern of an opposite adsorption preference [1]. In addition to a variation of the substrate properties we can also modify the particle's surface properties by adsorption of thiols with different terminal groups. Due to the interplay of lateral and vertical critical Casimir forces, we observed very different colloidal structures.

[1] Critical Casimir forces in colloidal suspensions on chemically patterned surfaces F. Soyka et al. Phys. Rev. Lett., 101, 208301 (2008)