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Freiburger Materialforschungszentrum
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79104 Freiburg, Germany

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You are here: Home Events Hong Xu "Kinetics and dynamic properties of cylindric micelles at equilibrium and under shear flow"

Hong Xu "Kinetics and dynamic properties of cylindric micelles at equilibrium and under shear flow"

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Laboratoire de Physique des Milieux Denses (LPMD) Université Paul Verlaine - Metz

What
  • Seminar
When Dec 01, 2010
from 02:15 PM to 03:00 PM
Where “Hörsaal Makromolekulare Chemie”, Stefan-Meier-Str. 31, Freiburg
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Abstract

The dynamics and rheology of semi-dilute unentangled micellar solutions are investigated by Langevin dynamics mesoscopic simulations coupled to a microreversible kinetic model for scissions and recombinations. Two equilibrium state points, differing by the scission energy and therefore by the corresponding average micelle length, have been examined. The kinetic rates are tuned by an independent parameter of the model, whose range is chosen in such a way that the kinetics always strongly couple to the chain dynamics.

Our results confirm, as predicted by Faivre and Gardissat, that the stress relaxation, as well as the monomer diffusion, is characterized by a time tL, defined by the life time of a segment L, whose Rouse relaxation time is equal to its life time. Moreover, the power law  dependence of the zero-shear viscosity versus tL was evidenced. Non-equilibrium simulations show that the chain deformation and orientation, as well as the rheology of the system, can be expressed as universal functions of a single reduced shear rate which is the bare shear rate multiplied by tL. Furthermore, local analysis of the kinetics under stationary shear gives insights on the variation of the average length with shear rate.

 

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