By: Nuno Silvestre
At: Complexo Interdisciplinar, Anfiteatro
Colloidal dispersions in liquid crystals are different from the ordinary colloids due to the long-range orientational order of the liquid crystal molecules. In addition, colloidal particles present complex interactions that have a long-range dipolar or quadrupolar profile that are an important feature needed to self-organise into supermolecular structures specific of colloidal liquid crystals. The structures observed in experiments are stabilized by the presence of topological defects that induce complex short-range repulsions. Future applications of liquid crystal colloids involve colloidal optical materials, where the complex anisotropic properties of liquid crystals is combined with the optical response of colloidal dispersions, and supercapacitors, by the addition of suitable nano-particles.
Liquid crystal colloids are present also as (quasi-) two-dimensional systems and their study can give further understanding of their three-dimensional equivalents. We will talk about colloid-colloid interactions in 2d liquid crystal systems. In particular, we will show the role of topological defects in stabilising their equilibrium configurations. We will talk also on the interaction between colloidal particles and the confining walls and, in particular, we will foccus on the key-lock mechanism present in these systems. Finally, we will show how the liquid crystal can act on the shape of soft colloidal particles.