A Monte-Carlo study of equilibrium polymers in a shear flow |
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Authors: | A Milchev JP Wittmer DP Landau |
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Institution: | (1) Institute for Physical Chemistry, Bulgarian Academy of Sciences, 1113Sofia, Bulgaria, BG;(2) Département de Physique des Matériaux, Université Claude Bernard Lyon I, 69622 Villeurbanne Cedex, France, FR;(3) Department of Physics and Astronomy, University of Georgia, Athens, Ga. 30602, USA, US |
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Abstract: | We use an off-lattice microscopic model for solutions of equilibrium polymers (EP) in a lamellar shear flow generated by means
of a self-consistent external field between parallel hard walls. The individual conformations of the chains are found to elongate
in flow direction and shrink perpendicular to it while the average polymer length decreases with increasing shear rate. The
Molecular Weight Distribution of the chain lengths retains largely its exponential form in dense solutions whereas in dilute
solutions it changes from a power-exponential Schwartz distribution to a purely exponential one upon an increase of the shear
rate. With growing shear rate the system becomes increasingly inhomogeneous so that a characteristic variation of the total
monomer density, the diffusion coefficient, and the center-of-mass distribution of polymer chains of different contour length
with the velocity of flow is observed. At higher temperature, as the average chain length decreases significantly, the system is shown to undergo an order-disorder transition
into a state of nematic liquid crystalline order with an easy direction parallel to the hard walls. The influence of shear
flow on this state is briefly examined.
Received 22 October 1998 and Received in final form 12 April 1999 |
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Keywords: | PACS 83 50 Ax Steady shear flows[:AND:]82 35 +t Polymer reactions and polymerization - 61 25 Hq Macromolecular and polymer solutions polymer melts swelling - 64 60 Cn Order disorder transformations statistical mechanics of model systems |
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