Santoni-Ortiz, Christian J.
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Publication Brownian dynamics simulation of colloidal particles in a Gay-Berne suspension(2013) Santoni-Ortiz, Christian J.; Gutiérrez, Gustavo; College of Engineering; Leonardi, Stefano; Cancelos, Silvina; Córdova-Figueroa, Ubaldo M.; Department of Mechanical Engineering; Román Pérez, Rosa I.Complex colloidal fluids have become an emerging composite material useful for novel industrial and technological applications. The dispersion of colloids in anisotropic fluids with crystal-like structures, such as nematic liquid crystals, it is of particular interest for the developing of new sensor technologies. Experiments have shown the presence of colloidal particles in these fluids induce the formation of topological defects due to the disruption of the director of the nearby molecules which propagate through the medium. The type of defect which occurs in a liquid crystal depends on the orientation the molecules adopt around the colloid, either parallel or tangential to its surface, which in turn depends on the functionalization over the particle surface. The presence of multiple colloids induces chain-like aggregations and for higher colloid concentrations, the formation of network-like structures in the liquid crystal. This aggregation is the result of the minimization of energy of the suspension caused by the presence of topological defects. This phenomena is studied from a coarse-grained perspective, through Brownian dynamics simulations in order to understand the role of the topological defects in the mobility and aggregation of particles. Studying liquid crystal colloids from this perspective extent the time and length scale of the simulations, providing the possibility of studying macroscopic rheological properties. In order to accomplish our goals, the long-time self-diffusivity of a single colloid immersed in a suspension of prolates spheroids that interacts through the Gay-Berne potential for volume fractions which range from φ = 0.05 − 0.70 for homeotropic and tangential anchoring is studied. The anchorings are controlled through the colloid-rod potential developed by Antypov et al. [1]. The long-time self-diffusivity of the colloidal particle obtained in an isotropic phase was of D∞ ∼ 0.30Do for homeotropic anchoring and D∞ ∼ 0.57Do for tangential anchoring, which can be attributed to the added volume of the ellipsoids to the colloidal particle. A percent difference of 62% and 68% of the long-time self-diffusivity parallel and perpendicular, respectively, between the nematic and isotropic phase was found. In addition, the interaction forces between two spherical colloids as a function of the separation distance for homeotropic and tangential anchoring over both particles was calculated. It was found that the interaction for the homeotropic anchoring was an order of magnitude higher than the tangential one, while in the nematic phase the interaction was of longer range than in the isotropic phase.