Dynamics of colloidal cubes and cuboids in cylindrical nanopores

Abstract

Understanding how colloidal suspensions behave in confined environments has a striking relevance in practical applications. Despite the fact that the behavior of colloids in the bulk is key to identifying the main elements affecting their equilibrium and dynamics, it is only by studying their response under confinement that one can ponder the use of colloids in formulation technology. In particular, confining fluids of anisotropic particles in nanopores provides an opportunity to control their phase behavior and stabilize a spectrum of morphologies that cannot form in the bulk. By properly selecting the pore geometry, particle architecture, and system packing, it is possible to tune their thermodynamic, structural, and dynamical properties for ad hoc applications. In the present contribution, we report Grand Canonical and Dynamic Monte Carlo simulations of suspensions of colloidal cubes and cuboids constrained into cylindrical nanopores of different sizes. We first study their phase behavior, calculate the chemical potential vs density equation of state, and characterize the effect of pore walls on particle anchoring and layering. In particular, at large enough concentrations, we observe the formation of concentric nematic-like coronas of oblate or prolate particles surrounding an isotropic core, whose features resemble those typically detected in the bulk. We then analyze the main characteristics of their dynamics and discover that these are dramatically determined by the ability of particles to diffuse in the longitudinal and radial directions of the nanopore.