Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 7: SYMPOSIUM Disperse Polymer Systems I
CPP 7.5: Invited Talk
Tuesday, March 28, 2006, 11:00–11:30, ZEU 160
Non-linear rheological properties of glassy colloidal dispersions — •Matthias Fuchs1, Oliver Henrich1, Michael Cates2, Matthias Ballauff3, Jerome Crassous3, and Fathollah Varnik4 — 1Fachbereich Physik, Universitaet Konstanz — 2School of Physics, The University of Edinburgh — 3Physikalische Chemie I, Universitaet Bayreuth — 4MPI fuer Eisenforschung, Duesseldorf
Soft materials, such as particle dispersions, quite universally exhibit a strongly decreasing viscosity as function of shear rate (’shear thinning’). We study theoretically an universal mechanism explaining the reduction of the viscosity or stress in such disordered colloidal systems.
Our first-principles approach [1] to the non-linear rheology of dense colloidal suspensions predicts an universal transition between the yielding of amorphous solids and non-Newtonian (shear-thinning) fluid flow. The approach builds upon a microscopic description of structural relaxations in quiescent suspensions provided by the mode coupling theory. The advection of density fluctuations is the dominant mechanism captured, while hydrodynamic interactions, non-linear flow profiles and ordering phenomena are neglected. Comparisons with experiments in model colloidal dispersions support the approach [2], as do computer simulations of Newtonian supercooled liquids, which find a finite dynamic yield stress at low temperatures [3].
[1] M. Fuchs and M. E. Cates, Phys. Rev. Lett. 89, 248304 (2002); Faraday Discuss. 123, 267 (2003); J. Phys.: Condens. Matter 17, 1681 (2005)
[2] M. Fuchs and M. Ballauff, J. Chem. Phys. 122, 094707 (2005)
[3] F. Varnik and O. Henrich, submitted (2005)