Interplay of anisotropy in shape and interactions in charged platelet suspensions

Abstract

Motivated by the intriguing phase behavior of charged colloidal platelets, we investigate the structure and dynamics of charged repulsive disks by means of Monte-Carlo simulations. The electrostatic interactions are taken into account through an effective two-body potential, obtained within the nonlinear Poisson-Boltzmann formalism, which has the form of anisotropic screened Coulomb potential. Recently, we showed that the original intrinsic anisotropy of the electrostatic potential in competition with excluded volume effects leads to a rich phase behavior that not only includes various liquid-crsytalline phases but also predicts the existence of novel structures composed of alternating nematic-antinematic sheets. Here, we examine the structural and dynamical signatures of each of the observed structures for both translational and rotational degrees of freedom. Finally, we discuss the influence of effective charge value and our results in relation to experimental findings on charged platelet suspensions.

Isotropic, nematic, and lamellar phases in colloidal suspensions of nanosheets

“…Moreover, there have only been a few theoretical studies of the phase diagram of electrically charged plate-like particles reported so far because the electrostatic interaction potential of two charged disks in suspension has only recently been calculated ( 45 ). Based on this potential, numerical simulations were made to draw rich phase diagrams that present the nematic and columnar phases, among others, but not the lamellar one ( 10 , 46 ).…”

Empty smectic liquid crystals of hard nanorings: Insights from a second-virial theory

“…The second surprising feature is that the rings are ordered antinematically, that is, the particle vectors preferentially lie in a plane perpendicular to the nematic director, contrary to what is found in most discotic liquid crystals. Evidence of antinematicity was found in some soft-interaction models for clay particles [21] and deformable dendrimers [22]. It is quite surprising to see this type of order emerging in simple systems of nanorings which interact only through steric repulsion without the need to apply an external field [23].…”

Synthesis and applications of anisotropic nanoparticles with precisely defined dimensions

“…[192][193][194] A full understanding of their rheological behaviour therefore requires a combination of theory, molecular modelling and experimental work. Developments in the theoretical understanding of these systems have suggested a rich interplay between the effects of shape and other properties such as charge, 18,196 enabling complex and potentially useful behaviours to be realised. However, examples of empirical studies in which the dimensions of nanoparticles are systematically varied are rare, possibly because this field has traditionally made use of particles such as clay nanosheets, for which well-controlled syntheses have yet to be developed.…”