(87c) Kinetics and Thermodynamics of Colloidal Particle Assembly

Colloidal particles can assemble into a myriad of structures by virtue of the many interaction forces available to them. Variable-range attraction and repulsion and the recently explored non-isotropic character, exemplified by Janus  and lock-and-key particles, are examples of the versatility of colloidal particles as building blocks. We explore the development of a systematic approach to understand the thermodynamics and kinetics of assembly of such particles, as a function of Janus balance, lock-and-key geometry, particle concentration, and gravitational and flow fields. A secondary goal of this work is the assessment of re-configurability of the structures found. To carry out these studies, anisotropic potentials and full lubrication and far-field hydrodynamic interactions are considered.   Our results show the range of stability of several structures, including a fluid phase of small clusters, bilayers and worm-like aggregates. We find the bilayer structures are very stable over a range of phase space and provide a good pre-cursor to hexagonally close-packed structures. We also use Brownian dynamics simulations with hydrodynamic interactions to examine the rates of formation of particle pairs under the action of shear fields of arbitrary strength, extending the classic work of Feke and Schowalter, which requires use of special boundary conditions and periodic box dimensions.  These findings enable the understanding of the assembly process of particles with both spherically symmetric and anisotropic particle interactions and provide a framework with which to study the kinetics of structure change.