Eur. Phys. J. E 6, 201-209 (2001)

Gels at interfaces

J.F. Joanny¹, A. Johner^{1, 2} and T.A. Vilgis<sup>1, 2

1</sup>  Laboratoire Européen Associé, Institut Charles Sadron, 6, rue Boussingault, F-67083 Strasbourg, Cedex, France
²  Laboratoire Européen Associé, Max Planck Institut für Polymer Forschung, P.O. box 3148, 55021 Mainz, Germany

johner@ics.u-strasbg.fr

(Received 16 July 2001)

Abstract
We discuss the adsorption of polymer gels on flat surfaces. Even in cases of complete wetting where the spreading power S is positive and where an equivalent liquid would spread, the elastic stresses due to the gel deformation upon adsorption oppose the spreading. The competition between elasticity characterized by the bulk shear modulus G and capillarity characterized by the spreading power S defines a typical length scale for the deformation in the gel. For loose gels can be of the order of . Macroscopic gels larger than deform only at their edges over a region of size . Microscopic gels smaller than show a finite deformation despite the elastic stresses. The elastic stresses limit the spreading of the polymer, but solvent can be sucked out of a swollen gel by wetting the surface. The thin solvent film can extend rather far from the gel edge and carry solvent. We calculate the kinetics of the solvent film formation and of the solvent transfer from a more swollen gel to a less swollen gel.

PACS
82.70.Gg - Gels and sols.
61.25.Hq - Macromolecular and polymer solutions; polymer melts; swelling.
68.45.Gd - Wetting.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001