Phase behavior of charged colloidal disks
By: Sara Jabbari
From: Université Paris-Sud
At: Instituto de Investigação Interdisciplinar, Anfiteatro
[2012-05-08]
Charged disks (platelets) are known as a model system for clay particles. Clay minerals suspended in water have an important impact in industry due to their ability to form yield stress fluids that confer solidity to soils, building materials and pharmacological products. The anisotropic plate-like shape of clay minerals, suggests that these materials could form liquid crystalline phases due to the competition between positional and orientational entropy. In practice, however, isotropic-nematic transition is hindered by formation of a gel-like viscoelastic phase in most of clays. Motivated by these experimental observations in clays, we have performed an extensive study of phase behavior of charged disks by means of Monte-Carlo simulations. The electrostatic interaction potential between charged disks surrounded by ions is taken into account by means of an anisotropic screened coulomb potential. We find that the orientationally-ordered liquid crystalline phases of charged disks appear at higher densities compared to that of nematic phase of hard disks. Furthermore, the anisotropy of potential destroys the nematic ordering; instead various types of columnar phases appear at high densities. In this talk, I will discuss the overall picture of phase behavior of as a function of screening parameter and density of disks.