Self-assembly of colloidal particles into ordered structures is hailed as the preferred route to production of functional devices on the nanometre and micron length scales. The shape of a colloidal particle is one of the most influential factors determining the type of ordered structure that is assembled. Thus this thesis is devoted to understanding the role of particle shape on phase behaviour of colloidal systems. The effect of particle shape is isolated by using computer simulations to model particles as hard, anisotropic bodies which interact via purely repulsive interactions. Two particle models are studied which are representative of real colloids: non-convex wireframe polyhedra, and convex spherical caps. This thesis investigates the densest packings of several wireframe polyhedra. By comparing packings of six distinct polyhedra some general conclusions are drawn regarding the effects of rounded polyhedra edges, and a new shape descriptor is given which can suggest whether a wireframe polyhedron is likely to form new interpenetrating crystal structures. Wireframe cubes were studied in more detail, where the full phase behaviour was mapped out. A curious phenomenon was found whereby crystals formed by cubic wireframes exhibit plastic fluctuations. This unusual behaviour, if reproduced experimentally, may lead to useful optical properties. A systematic study of spherical caps demonstrates the effect of shape on collective behaviour as the particle model interpolates between a sphere and a thin platelet. Purely repulsive interactions are responsible for a range of different crystal structures, but the nucleation of these structures is challenging due to slow dynamics. Furthermore, there are often many ways for a spherical cap to pack in a given volume, which leads to multiple metastable states. The self-assembly of spherical caps was directed by sedimentation on a solid template which resulted in increased nucleation rates and more stable crystals. However, there is still a lack of control over the exact crystal structure due to the degeneracy in ways to pack.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:734244 |
| Date | January 2017 |
| Creators | Mcbride, John |
| Contributors | Siperstein, Flor |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/computer-simulations-of-anisotropic-colloidal-particles(7c516a14-1be0-4450-a703-7048937f66d0).html |
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