The polymer mat: Arrested rebound of a compressed polymer layerU. Raviv1, J. Klein1, 2 and T.A. Witten3
1 Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
2 Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, UK
3 James Franck Institute, University of Chicago, Chicago IL 60637, USA
(Received 15 January 2002 and Received in final form 5 September 2002 / Published online: 25 February 2003)
Compression of an adsorbed polymer layer distorts its relaxed structure. Surface force measurements from different laboratories show that the return to this relaxed structure after the compression is released can require tens of minutes and that the recovery time can grow rapidly with molecular weight. We argue that the arrested state of the free layer before relaxation can be described as a Guiselin brush structure (O. Guiselin, Europhys. Lett. 17, 225 (1992)), in which the monomer density falls off only weakly with distance from the surface. This brush structure predicts an exponential falloff of the force at large distance with a decay length that varies as the initial compression distance to the 6/5 power. This exponential falloff is consistent with surface force measurements. We propose a relaxation mechanism that accounts for the increase in relaxation time with chain length.
68.47.Pe - Langmuir-Blodgett films on solids, polymers on surfaces, biological molecules on surfaces.
82.35.Gh - Polymers on surfaces; adhesion.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002