Adsorption of polyelectrolytes on silica and gold surfaces

TL;DR

This study uses dissipative particle dynamics simulations to analyze how cationic polyelectrolytes of different sizes adsorb onto silica and gold surfaces, revealing complex electrostatic and steric interactions affecting adsorption.

Contribution

It provides new insights into the adsorption mechanisms of polyelectrolytes on different surfaces, highlighting the roles of charge, chain length, and excluded volume effects.

Findings

Negatively charged walls do not always adsorb more cationic polyelectrolytes.

Larger polyelectrolyte chains have greater excluded volume, influencing adsorption.

Adsorption is driven mainly by excluded volume effects rather than electrostatic attraction.

Abstract

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.