Dynamics and evaporation-driven assembly in colloidal suspensions consisting of shape-isotropic and shape-anisotropic particles

Abstract

Colloidal systems are ubiquitous in nature and are found in many scientific and practical applications. Therefore, understanding their dynamical and assembly properties is key to comprehend their collective behavior and to unlock their potential in practical applications. In this thesis, we used molecular dynamics (MD) simulations to study the transport properties in colloidal suspensions and the evaporation--driven assembly of colloidal particles to form superstructures.

First, we investigated the presence of hydrodynamic interactions in colloidal suspensions using multi--particle collision dynamics coupled with a discrete particle model for the colloidal particles (MPCD). We compared the MPCD simulations with experimental data and other simulation methods such as Brownian dynamics with free--draining hydrodynamics (BD) and with far--field hydrodynamics using the Rotne--Prager--Yamakawa mobility tensor (RPY). We found that the MPCD simulations exhibited long--time self--diffusion and sedimentation coefficients that were comparable with experiments, showing that the MPCD method is a robust and simple method for modeling colloidal suspensions with hydrodynamic interactions. Additionally, we extended the discrete particle model to probe the influence of particle shape on their transport properties, examining shapes such as spheres, cubes, tetrahedra, octahedra and spherocylinders. Agreement of the simulation results with experimental data, where available, demonstrated the applicability of the discrete particle model to describe shape--anisotropic colloidal suspensions. Furthermore, we found that the self--diffusion of polyhedral shapes can be effectively estimated from its spherical analogue whose diameter is mean of the inscribed and circumscribed sphere diameters.

Second, we probed the structure formation in supraparticles fabricated from the evaporation of colloidal droplets containing elongated and/or spherical particles. We found that the orientational ordering and packing of the elongated particles in supraparticles can be controlled through the evaporation rate and aspect ratios of the rod--like particles.