Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 7: POSTERS Rheology

CPP 7.21: Poster

Montag, 25. Februar 2008, 16:45–19:00, Poster A

Network induced relaxation dynamics in colloidal gels. — •Emanuela Del Gado — Polymer Physics, ETH Zürich

In contrast to other systems that show a slow relaxation, such as, e.g., glass-forming liquids, the structure of gels is given by a open network that is thought to be responsible for the unusual dynamical properties of these systems. It would be therefore essential to deeper understand this connection and to be able to tune the mechanical response via the structural features. We investigate the gel formation from the equilibrium sol phase in a simple model that has the characteristics of (colloidal) gel-forming systems at a finite temperature [1]. In the molecular dynamics simulations, at low volume fraction and low temperatures, particles are linked by long-living bonds and form an open percolating network. As a consequence, the dynamics show a non-trivial dependence on the wave-vector: At high wave vectors the relaxation is due to the fast cooperative motion of the branches of the gel network, whereas at low wave vectors the overall rearrangements of the heterogeneous structure produce the relaxation process. We study the lifetime of bonds and nodes of the gel network in order to relate these quantities to the complex relaxation dynamics observed. [1]E. Del Gado and W. Kob, Europhys. Lett. 71, 1032 (2005); Phys. Rev. Lett. 98, 028303 (2007); J. Non-Newt. Fluid Mech. 2007, in press.