30 Sara Llamas, Laura Fernández-Peña, Ana Mateos-Maroto et al.
Therefore, the understanding of the different variables (e.g., ionic
strength, pH, temperature, etc.) that modify the balance of interactions
governing the adsorption of polyelectrolytes is a scientific challenge for
both basic and applicative purposes. The aforementioned variables are
mainly related to the modification of the charge density of both polymer
and surface, playing a key role on the control of the different
contributions involved in the formation of the layers: electrostatic,
specific, entropic, etc. This Chapter presents a comprehensive study of
the complex physico-chemistry associated with the adsorption of
polyelectrolyte layers, both single layer or multilayers formed for
oppositely charged polyelectrolytes, onto solid surface, paying special
attention to the adsorption of polyelectrolytes onto charged surfaces.1. INTRODUCTION
The interaction of macromolecules (synthetic polymers, polyelectrolytes,
proteins, and/or colloidal nanoparticles) and surfactants with interfaces and
surfaces is a topic with an increasingly interest due to their recognized
implication in many scientific and technological areas including cosmetic,
pharmaceutical and nutriceutical products, fabrication of functional materials
and coatings, paints, anti-icing liquids, tertiary oil recovery, and paper industry
[1-6]. This is due to the ability of those molecules for modifying some of the
properties of the surfaces, e.g., lubrication, hydration, mechanical properties,
resistance against corrosion [7], which have driven many research efforts, both
theoretical and experimental, for understanding the adsorption phenomena
associated with the interaction of polymers and colloids with surfaces,
especially solid ones [8-15].
The control and optimization of the aforementioned applications
require deepening on the physico-chemical aspects underlying the adsorption
processes. However, we are far from achieving a comprehensive
understanding of the different phenomena involved in the polymer - surface
interactions. The final structure of polymer layers is the result of an intricate
balance of interactions whose careful control has become a key issue for both
basic and applicative purposes. This is especially true in those cases in which
the interactions of polyelectrolyte with charged surfaces are considered [16-
18].
The adsorption of polyelectrolytes onto charged surfaces is mainly
governed by electrostatic interactions, which can be modified by several
variables, affecting to the adsorption process [19-21]. Among these variables