Dresden 2009 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Colloids

CPP 24.5: Vortrag

Mittwoch, 25. März 2009, 15:00–15:15, ZEU 160

Influence of the attraction range on the reentrant glass transition in colloid polymer mixtures — •Carl Stilke and Eckhard Bartsch — Institut f. Physikal. Chemie, Universität Freiburg, Albertstr. 21, D-79104 Freiburg

Recently the occurrence of a reentrant glass transition has been observed in a binary mixture of polystyrene microgel colloids in a good, isorefractive solvent to which linear polystyrene with a size ratio δ = Rg(polymer)/R(colloid) = 0.08 was added [1] to introduce depletion attractions. This phenomenon has been predicted by mode coupling theory (MCT) for such systems [2]. MCT predicts further that for smaller size ratios δ the reentry effect should become even stronger and that for δ > 0.0465 there should emerge a glass-glass transition line ending in a critical point (a A3 singularity in the MCT language).

To check up on these predictions we prepared colloid-polymer mixtures with a size ratio δ = 0.03. The short range order and the dynamics of these colloid-polymer mixtures were then studied with light scattering techniques in order to localize the glass transition lines. As the glass-glass transition line should be most easily detectable by a discontinuous jump in the plateau modulus Gp the rheological behaviour was studied as well. The obtained results are contrasted with the predictions of MCT.

[1] T. Eckert, E. Bartsch, J. Phys.: Condens. Matter 16, S4937,(2004) [2] K. Dawson etal., Phys. Rev. E 63, 011401, (2001)