Abstract
We develop a scaling theory of adsorption of necklace-like hydrophobic
polyelectrolytes at an oppositely charged hydrophilic and hydrophobic
surfaces. At low surface charge densities we predict a two-dimensional
adsorbed layer with thickness determined by the balance between electrostatic
attraction to the charged surface and chain entropy. At high surface
charge densities we expect a 3-dimensional layer with polymer density
profile determined either by the balance between two-body monomer-monomer
attraction or by electrostatic attraction to the surface and three-body
monomer-monomer repulsion. These different stabilizing mechanisms
result in the nonmonotonic dependence of the layer thickness on the
surface charge density. For adsorption of polyelectrolyte chains
from salt solutions the screening of the electrostatic repulsion
between adsorbed polyelectrolyte chains results in large overcompensation
of the surface charge for two-dimensional adsorbed layers. The polymer
surface coverage for this regime increases with increasing salt concentration.
The opposite trend is predicted for 3-D adsorbed layers where the
polyelectrolyte surface excess decreases with increasing salt concentration.
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