Dynamics of Colloidal Cubes and Cuboids in Cylindrical Nanopores

TL;DR

This study uses Monte Carlo simulations to explore how colloidal cubes and cuboids behave in cylindrical nanopores, revealing phase transitions, particle layering, and diffusion dynamics influenced by confinement.

Contribution

It provides new insights into the phase behavior and dynamics of anisotropic colloids in nanopores through detailed simulation analysis.

Findings

Formation of concentric nematic-like coronas around isotropic cores.

Particle diffusion is highly affected by pore geometry and confinement.

Phase behavior in nanopores can resemble bulk properties under certain conditions.

Abstract

Understanding how colloidal suspensions behave in confined environments has a striking relevance in practical applications. Despite the fact that the behaviour of colloids in the bulk is key to identify 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 the opportunity to control their phase behaviour and stabilise a spectrum of morphologies that cannot form in the bulk. By properly selecting pore geometry, particle architecture and system packing, it is possible to tune 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 size. We first study their phase behaviour, calculate the chemical potential vs density equation of state and characterise the effect of the 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 analyse 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 direction of the nanopore.