Effective potentials in crowded environments

NICOLÁS A. GARCÍA; NICOLETTA GNAN; EMANUELA ZACCARELLI

Roma

Conferencia; 30th Conference of The European Colloid and Interface Society; 2016

Effective interactions play an important role in the physics of colloidal dispersions. The most established way to tune effective potentials is by means of depletion [1,2]. More recently, effective forces modified by the spontaneous self‐assembly of the co‐solute have been studied, with critical Casimir‐like forces being a famous example [3,4]. In this talk, we examine the effective forces generated by a co‐solute which self‐organizes into linear chains (see Fig. 1) or larger aggregates. We use 3D Monte Carlo simulations to calculate the effective potential between two large colloids immersed in a solution composed of depletant particles ten times smaller. These particles are modelled as patchy colloids in which a hard‐core repulsion is complemented by two or more short‐ranged attractive 'sticky' spots [5]. At high cosolute densities, we find that the effective potentials, despite being purely attractive, display unusual peaks. We associate these peaks with enhanced ordering of the co‐solute, e.g. nematic for assembled linear chains, at characteristic distances, due to the confinement operated by the colloids. Our study paves the way for a new class of colloidal interactions occurring in crowded environments and biologically relevant systems.