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Issue 15, 2012

Semidilute solutions of ultra-soft colloids under shear flow

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Abstract

We study semidilute star-polymer solutions under shear flow by hybrid mesoscale simulations. Hydrodynamic interactions are modeled by two particle-based simulation techniques, multiparticle collision dynamics (MPC) and dissipative particle dynamics (DPD). Star polymers are considered as a paradigmatic model for ultra-soft colloids with variable softness. The influence of concentration and shear rate on their structural and rheological properties is investigated. Under flow, a star polymer elongates and displays a well-defined alignment angle with respect to the flow direction. Moreover, the structural and rheological properties exhibit a universal behavior as a function of a concentration-dependent Weissenberg number for various concentrations at a given arm length. The rheological properties are characterized by the shear viscosity and the normal-stress coefficients. In dilute solution, the zero-shear viscosity follows the Einstein relation with an effective radius given by the hydrodynamic radius of a star polymer. At high shear rates, the solutions exhibit shear-thinning behavior, where the viscosity decreases faster with increasing shear rate at higher concentrations. We demonstrate that the results obtained from MPC and DPD agree in all scaling properties, with minor quantitative deviations in the numerical values.

Graphical abstract: Semidilute solutions of ultra-soft colloids under shear flow

Supplementary files

Article information


Submitted
20 Oct 2011
Accepted
05 Jan 2012
First published
26 Jan 2012

Soft Matter, 2012,8, 4109-4120
Article type
Paper

Semidilute solutions of ultra-soft colloids under shear flow

D. A. Fedosov, S. P. Singh, A. Chatterji, R. G. Winkler and G. Gompper, Soft Matter, 2012, 8, 4109 DOI: 10.1039/C2SM07009J

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