J. Phys. II France
Volume 5, Numéro 7, July 1995
Page(s) 1093 - 1103
DOI: 10.1051/jp2:1995226
J. Phys. II France 5 (1995) 1093-1103

Extension and Compression of Grafted Polymer Layers in Strong Normal Flows

J.L. Harden1, 2 and M.E. Cates2

1  Cavendish Laboratory, Cambridge University Madingley Road, Cambridge CB3 0HE, UK
2  Department of Physics and Astronomy, University of Edinburgh, J.C. Maxwell Building, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, UK

(Received 21 February 1995, accepted 27 March 1995)

We study the deformation of polymer brushes grafted to porous substrates in strong permeation flows normal to the grafting surface. Our model predicts a strong deformation regime for both compressive and extensive permeation flows of sufficiently high solvent flow rates. These regimes are characterized by non-linear scaling of brush thickness L with molecular weight N and solvent velocity V and by non-linear scaling of solvent velocity V with the pressure drop $\Delta P$ across the brush. For the case of strong brush extension, $L\sim N^3V^2$, as in the case of isolated chains in uniform solvent flows, and $V\sim \Delta P^{1/3}$; while for strong brush compression, $L\sim N^{9/13}V^{-4/13}$ and $V\sim \Delta P^{13/15}$.

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