Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: POSTERS Rheology
CPP 7.4: Poster
Montag, 25. Februar 2008, 16:45–19:00, Poster A
Shear induced brush deformation of soft colloids: Hybrid mesoscale simulations and Rheo-SANS experiments — •Jörg Stellbrink1, Marisol Ripoll1, Roland G. Winkler1, Gerhard Gompper1, Jan K.G. Dhont1, Dieter Richter1, Dimitris Vlassopoulos2, and Peter Lindner3 — 1IFF, Forschungszentrum Jülich, D-52425 Jülich — 2IESL-FORTH, Heraklion 71110 Crete, Greece — 3Institute Laue-Langevin, F-38042 Grenoble, France
The deformation of a soft colloid by external shear fields crucially depends on its "degree of softness" and the applied Weissenberg number. (Wi=τc γ, with γ the applied external shear rate and τc the characteristic internal relaxation time of the deformable particle.)
Here we compare results obtained with multiparticle collision dynamics simulations (MPC) and Rheo-SANS experiments for dilute solutions of regular star polymers (the limiting ultra-soft colloid). To achieve large Weissenberg numbers we use high Mw polybutadiene (PB) star polymers dispersed in a PB oligomer matrix. We found excellent agreement between theory and experiment with respect to onset and amount of shear induced brush deformation for star polymers with varying functionality f.
Moreover, from MPC simulations we found that with increasing functionality star polymers exhibit a crossover in their flow properties from those of linear polymers to a novel behavior, which resembles the tank-treading motion of elastic capsules [1].
[1] M. Ripoll, R. G. Winkler, and G. Gompper, Phys. Rev. Letters, 96, 188302, (2006).