  The results of a study that helps understand the mechanisms of adsorption of
polyelectrolytes on particles, using numerical simulation methods, specifically
the one known as dissipative particle dynamics are reported here. The
adsorption of cationic polyelectrolytes of two different polymerization degrees
interacting with two types of surfaces, one made of gold and the other of
silica is predicted and compared. We find that a more negatively charged wall
does not necessarily adsorb more cationic polyelectrolytes because the
electrostatic repulsion between the wall and the polyelectrolytes is stronger.
Additionally, intra chain repulsion plays an important role, because the
largest polyelectrolyte chains have larger excluded volume than the shorter
ones. In regard to the adsorption dependence on the polyelectrolyte
polymerization degree we find that the excluded volume drives the adsorption
throughout the intrachain electrostatic repulsion, because the SiO2 surface is
strongly negative. These results are expected to be useful for several
nanotechnological applications of current interest, such as in gene therapy and
in the improvement of drug delivering mechanisms.
