title: Measurement of long-ranged steric forces between polyelectrolyte layers physisorbed from 1 M NaCl.
abstract: The colloidal probe technique (CPT) is used to measure distance-dependent interaction forces between polyelectrolyte layers physisorbed from 1 M NaCl solution in salt solutions between 0.1 mM and 1 M. Both linear polycations (poly(allylamine)hydrochloride, poly-L-lysine) and linear polyanions (poly(styrenesulfonate)) are used. The repulsive interaction energies in the range between 10(-7) and 10(-4) J/m2 are described by the theory of Alexander and de Gennes for surfaces covered with neutral anchored polymers. However, the brush thickness scales with molecular area and salt concentration with a power of -1/3 as known from a salted brush and reaches approximately 50% of the contour length in diluted solutions. The findings are confirmed by CPT images using a gold layer as height reference.
authors.affiliation: Institut für Physik, Ernst-Moritz-Arndt Universität, Felix-Hausdorff-Strasse 6, D-17487 Greifswald, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Block
authors.forename: Christiane A
authors.initials: CA
authors.lastname: Helm