  For a tailored functionalization of cellulose based papers, the interaction
between paper fibers and functional additives have to be understood. Planar
cellulose surfaces present a suitable model system for studying the binding of
additives. In this work, polyelectrolyte multilayers (PEMs) as model surfaces
are prepared by alternating dip coating of the negatively charged cellulose
derivate carboxymethyl cellulose and a polycation, either PDADMAC or chitosan.
The varied parameters of the PEM formation are the polyelectrolyte
concentrations and pH (pH=2-6). Both PEM systems exhibit an exponential growth,
which reveals a high mobility of the polyelectrolytes (PEs). The pH-tunable
charge density leads to PEMs with different surface topographies. QCM-D
experiments reveal pronounced viscoelastic properties of the PEMs. Ellipsometry
and atomic force microscopy measurements show that the strong and highly
charged polycation PDADMAC leads to the formation of smooth PEMs. The weak
polycation chitosan results in cellulose model surfaces with higher film
thicknesses and a tunable roughness. The PEMs prepared from both polycations
exhibit a high water uptake when exposed to a humid environment. The resulting
PEMs are suitable water-stable but water swellable model surfaces with a
controllable roughness and topography.
