Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 1: DRG-DPG SYMPOSIUM Rheology I
CPP 1.2: Vortrag
Montag, 25. Februar 2008, 10:00–10:15, C 130
Shear stresses of colloidal dispersions at the glass transition in equilibrium and in flow — Jerome Crassous1, Miriam Siebenbürger1, •Matthias Ballauff1, Markus Drechsler2, David Hajnal3, Oliver Henrich3, and Matthias Fuchs3 — 1Physikalische Chemie I, Universität Bayreuth, 95440 Bayreuth — 2Makromolekulare Chemie II, Universität Bayreuth, 95440 Bayreuth — 3Fachbereich Physik, Universität Konstanz, 78457 Konstanz
We consider a model dense colloidal dispersion at the glass transition, and investigate the connection between equilibrium stress fluctuations, seen in linear shear moduli, and the shear stresses under strong flow conditions far from equilibrium, viz. flow curves for finite shear rates. To this purpose thermosensitive core-shell particles consisting of a polystyrene core and a crosslinked poly(N-isopropylacrylamide)(PNIPAM) shell were synthesized. Data over an extended range in shear rates and frequencies are compared to theoretical results from integrations through transients and mode coupling approaches. The connection between non-linear rheology and glass transition is clarified. While the theoretical models semi-quantitatively fit the data taken in fluid states and the predominant elastic response of glass, a yet unaccounted dissipative mechanism is identified in glassy states.