  We propose a theoretical investigation of the physical adsorption of neutral
comb-polymers with an adsorbing skeleton and non-adsorbing side-chains on a
flat surface. Such polymers are particularly interesting as "dynamic coating"
matrices for bio-separations, especially for DNA sequencing, capillary
electrophoresis and lab-on-chips. Separation performances are increased by
coating the inner surface of the capillaries with neutral polymers. This method
allows to screen the surface charges, thus to prevent electro-osmosis flow and
adhesion of charged macromolecules (e.g. proteins) on the capillary walls. We
identify three adsorption regimes: a "mushroom" regime, in which the coating is
formed by strongly adsorbed skeleton loops and the side-chains anchored on the
skeleton are in a swollen state, a "brush" regime, characterized by a uniform
multi-chains coating with an extended layer of non-adsorbing side-chains and a
non-adsorbed regime. By using a combination of mean field and scaling
approaches, we explicitly derive asymptotic forms for the monomer concentration
profiles, for the adsorption free energy and for the thickness of the adsorbed
layer as a function of the skeleton and side-chains sizes and of the adsorption
parameters. Moreover, we obtain the scaling laws for the transitions between
the different regimes. These predictions can be checked by performing
experiments aimed at investigating polymer adsorption, such as Neutron or X-ray
Reflectometry, Ellipsometry, Quartz Microbalance, or Surface Force Apparatus.
