Interplay between adsorption, aggregation and diffusion in confined core-softened colloids

Abstract

The behavior of colloidal particles with a hard core and a soft shell has attracted the attention for researchers in the physical-chemistry interface not only due to the large number of applications, but also owing to the unique properties of these systems, both in bulk and at interfaces. The adsorption at the two-phase boundary can provide information about the molecular arrangement. Thus, by Langevin Dynamics simulations, we have employed a recently obtained core-softened potential to analyze the relation between adsorption, structure and dynamic properties of the polymer-grafted nanoparticles near a solid repulsive surface. Two cases were considered: flat or structured walls. At low temperatures, a maximum is observed in the adsorption. It is related to a fluid to clusters transition and with a minimum in the contact layer diffusion - which is explained by the competition between the scales in the core-softened interaction. Due to the long range repulsion, the particles stay at the distance correspondent to this length scale at low densities, and overcome the repulsive barrier as the packing increases. However, by increasing the temperature, the gain in kinetic energy allows the colloids to overcome the long range repulsion barrier even at low densities. As a consequence, there is no competition and no maximum was observed in the adsorption.