Systems of colloids coated with high-information polymers are powerful tools for designing crystal lattice with tailorable properties or studying the fundamentals of crystallization. By changing the colloid-colloid interaction strength or colloid shape, different types of lattices can be assembled. In this thesis, I present novel coarse-grained models to describe high-information polymer coated', 'colloids in simulation and use various explicit chain models to study experimental systems.', 'Chapter 2 presents a static model based on orbital descriptions that enable calculation of arbitrary interaction potentials and colloid shape. This is intended to alleviate the need for explicit chains in coarse-grained simulations. I show that this model enables computation of assembly of Janus particles with charges on the surface interacting through Yukawa potential.', 'Chapter 3 extends this orbital model for time-varying orbitals based on an expansion around equilibrium. I revisit the pathological cases observed in assembly of polymer-coated cubes where shell deformation induces phase changes.', 'Chapter 4 presents the phases observed for various polyhedron colloids coated with deoxyribonuclic acid (DNA). Short DNA enforces packing according to the shape of particle core, while long DNA induces spherical-like packing. For cubes, we find that the system transitions from one cubic phase to another by breaking symmetry into a tetragonal phase. This is due to deformation', 'of the colloids’ DNA shells.', 'Chapter 5 presents kinetic Wulff shapes obtained from growth of hexagonal AB 2 type crystals, which grow in long hexagonal prisms. Unlike usual kinetic products, the shape is highly reproducible. We show that assembly into hexagonal rods happens due to energy barriers between different surface layers with identical Miller indices.', 'Chapter 6 presents a study on colloid crystal size obtained as a function of salt concentration. In particular, experiments find that the mean crystal size drastically increases when concentration is raised to 1M. Based on simulation results, we find that this is due to an increase of the attachment barrier between two colloids. This increase results in a slower attachment and nucleation rates,', 'which effectively means that diffusion is faster. The interface-limited to diffusion-limited transition for individual colloids thus happens at a larger crystallite size, resulting in a faster growth of individual colloids at constant nucleation rate.', 'Chapter 7 introduces the concept of metallic bonding in self-assembled crystals. Previously studied crystals had defined positions for all colloids in the crystal. By mixing the usual colloids with much smaller ones (≤ 2 nm), we find that these small particles stop holding defined crystallographic positions and instead roam the crystals, similar to electrons in a classical metal. We define metallicity as translation entropy of small particles and explain system behavior with analogies from band structure of solid-state physics. We also find that there is a Mott-like transition of these particles with changes in temperature. At low temperatures, the electron condensates in defined crystallographic positions corresponding to complex metal alloys or intermetallics.

Last modified

• 10/21/2019

Creator

• Martin Girard

DOI

• https://doi.org/10.21985/n2-m822-hj15

Subject

• Applied Physics

Keyword

• DNA
• molecular dynamics
• nanomaterials
• Colloidal crystallization

Date created

• 2018-01-01

Resource type

• Dissertation

Rights statement

• In Copyright