DOI: 10.1051/jp2:1997175
J. Phys. II France 7 (1997) 1111-1121

Forces between Surfaces with Weakly End-Adsorbed Polymers

J.I. Martin¹, Z.-G. Wang¹, D. Zuckerman², R. Bruinsma³ and P. Pincus<sup>4

1</sup>  Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
²  Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA
³  Department of Physics, University of California, Los Angeles, CA 90024, USA
⁴  Departments of Physics and Materials, University of California, Santa Barbara, CA 93106 USA

(Received 9 October 1996, revised 10 April 1997, accepted 22 April 1997)

Abstract
We study the interaction forces between two plates in a semi-dilute solution of polymers each having one weakly adsorbing end-group. We show that this system exhibits both repulsive and attractive interactions of comparable magnitude and well-separated length scales: when the plate separation is within a range of order the end-to-end distance of the end-adsorbed polymer, repulsion arises with a magnitude of where is the end-adsorption energy, N is the degree of polymerization, a is the Kuhn length and the volume fraction of the polymer. This repulsion is due to desorption of the end-adsorbed chains. At plate separations of order the correlation length of the solution, a depletion attraction sets in with a magnitude that scales with the bulk osmotic pressure.

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