Self-assembly scenarios of inverse patchy colloids

Abstract

Spontaneous self-assembly is a process in which a disordered system crystallizes into an ordered structure without external influence. In this work, we study the self-assembly properties of inverse patchy colloids (IPCs). IPCs were originally introduced to describe the complex colloids formed by the adsorption of polyelectrolyte stars onto charged colloids, however the proposed model of IPCs is very versatile and can be used to describe many real systems of colloids with a heterogeneously charged surface. We consider IPCs composed of a negatively charged central body and two positively-charged patches localised at the poles. The complex interplay between the regions of like and unlike charge makes the phase behavior of IPCs considerably more complex than the one typical of conventional patchy colloids. Using molecular dynamics simulation, we investigated the model by varying the charge distribution, the size of the patches, and the interaction range. Models with small patch extension did not spontaneously self-assemble into any ordered structue, thus we studied their fluid phase by means of integral equation theories. Models with medium patch extenstion crystallized in a novel hybrid crystal-liquid structure, that we characterized by means of correlation functions. Finally, models with large patch amplitudes formed a face centered cubic lattice.