Colloidal SU-8 rods and banana-shaped particles: synthesis and liquid crystal self-assembly
<p>In this thesis, we describe the development of two novel model systems of anisotropic colloidal particles and study their self-assembly into colloidal liquid crystal phases with confocal microscopy. In particular, we develop a system of colloidal rod-like and banana-shaped particles made of...
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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2021
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| _version_ | 1826297242657488896 |
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| author | Fernandez Rico, C |
| author2 | Dullens, R |
| author_facet | Dullens, R Fernandez Rico, C |
| author_sort | Fernandez Rico, C |
| collection | OXFORD |
| description | <p>In this thesis, we describe the development of two novel model systems of anisotropic colloidal particles and study their self-assembly into colloidal liquid crystal phases with confocal microscopy. In particular, we develop a system of colloidal rod-like and banana-shaped particles made of a polymeric material called SU-8. First, we describe the synthesis of colloidal SU-8 rods with tunable dimensions by using sonication. This simple yet, crucial step allows us to bring the SU-8 rod system -- which had been limited to the granular scale -- into the colloidal
domain. Crucially, these rods can be fluorescently labelled and are stable in both aqueous and non-aqueous solvents. Also, their refractive index and density mismatch with the solvent can be carefully controlled. As a result, the liquid crystal behaviour exhibited by the rods can be controlled and addressed in three dimensions using confocal microscopy whilst tuning the effect of gravity. Next, we describe the synthesis of colloidal SU-8 bananas by heating the originally straight SU-8 rods. Importantly, we demonstrate that the curvature of the bananas can be controlled by tuning the rigidity of the rods. This has an enormous impact on the liquid crystal phases the colloidal bananas exhibit with respect to the colloidal rods, as the particles are now biaxial. Using confocal microscopy, we next address the liquid crystal phase behaviour of the colloidal bananas, and how it is a�ected by curvature, at the single-particle level. We find a library of exotic liquid crystal phases, including polar and antipolar smectic phases and even the
elusive long-predicted splay-bend nematic phase. We then exploit the inherent polydispersity of the colloidal bananas to demonstrate that a hierarchical structure called the vortex phase can be assembled from polydisperse building blocks interacting via simple entropic interactions. We uncover the formation mechanism and the underlying geometrical principles dictating the structure of this hierarchical phase by systematically changing the curvature of the constituent bananas and characterising the resulting structures with confocal microscopy. Finally, we describe the fabrication of rough SU-8 rods and bananas with tunable asperity density via the nanoprecipitation of SU-8 nanospheres. With these newly developed rough particles, we provide two colloidal model systems for addressing surface-roughness related phenomena in materials composed of anisotropic particles.</p> |
| first_indexed | 2024-03-07T04:28:35Z |
| format | Thesis |
| id | oxford-uuid:cd844984-8f01-4f38-8eef-cdd4c9f29589 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T04:28:35Z |
| publishDate | 2021 |
| record_format | dspace |
| spelling | oxford-uuid:cd844984-8f01-4f38-8eef-cdd4c9f295892022-03-27T07:29:17ZColloidal SU-8 rods and banana-shaped particles: synthesis and liquid crystal self-assemblyThesishttp://purl.org/coar/resource_type/c_db06uuid:cd844984-8f01-4f38-8eef-cdd4c9f29589nanostructured materialsliquid crystalsColloidsEnglishHyrax Deposit2021Fernandez Rico, CDullens, R<p>In this thesis, we describe the development of two novel model systems of anisotropic colloidal particles and study their self-assembly into colloidal liquid crystal phases with confocal microscopy. In particular, we develop a system of colloidal rod-like and banana-shaped particles made of a polymeric material called SU-8. First, we describe the synthesis of colloidal SU-8 rods with tunable dimensions by using sonication. This simple yet, crucial step allows us to bring the SU-8 rod system -- which had been limited to the granular scale -- into the colloidal domain. Crucially, these rods can be fluorescently labelled and are stable in both aqueous and non-aqueous solvents. Also, their refractive index and density mismatch with the solvent can be carefully controlled. As a result, the liquid crystal behaviour exhibited by the rods can be controlled and addressed in three dimensions using confocal microscopy whilst tuning the effect of gravity. Next, we describe the synthesis of colloidal SU-8 bananas by heating the originally straight SU-8 rods. Importantly, we demonstrate that the curvature of the bananas can be controlled by tuning the rigidity of the rods. This has an enormous impact on the liquid crystal phases the colloidal bananas exhibit with respect to the colloidal rods, as the particles are now biaxial. Using confocal microscopy, we next address the liquid crystal phase behaviour of the colloidal bananas, and how it is a�ected by curvature, at the single-particle level. We find a library of exotic liquid crystal phases, including polar and antipolar smectic phases and even the elusive long-predicted splay-bend nematic phase. We then exploit the inherent polydispersity of the colloidal bananas to demonstrate that a hierarchical structure called the vortex phase can be assembled from polydisperse building blocks interacting via simple entropic interactions. We uncover the formation mechanism and the underlying geometrical principles dictating the structure of this hierarchical phase by systematically changing the curvature of the constituent bananas and characterising the resulting structures with confocal microscopy. Finally, we describe the fabrication of rough SU-8 rods and bananas with tunable asperity density via the nanoprecipitation of SU-8 nanospheres. With these newly developed rough particles, we provide two colloidal model systems for addressing surface-roughness related phenomena in materials composed of anisotropic particles.</p> |
| spellingShingle | nanostructured materials liquid crystals Colloids Fernandez Rico, C Colloidal SU-8 rods and banana-shaped particles: synthesis and liquid crystal self-assembly |
| title | Colloidal SU-8 rods and banana-shaped particles: synthesis and liquid crystal self-assembly |
| title_full | Colloidal SU-8 rods and banana-shaped particles: synthesis and liquid crystal self-assembly |
| title_fullStr | Colloidal SU-8 rods and banana-shaped particles: synthesis and liquid crystal self-assembly |
| title_full_unstemmed | Colloidal SU-8 rods and banana-shaped particles: synthesis and liquid crystal self-assembly |
| title_short | Colloidal SU-8 rods and banana-shaped particles: synthesis and liquid crystal self-assembly |
| title_sort | colloidal su 8 rods and banana shaped particles synthesis and liquid crystal self assembly |
| topic | nanostructured materials liquid crystals Colloids |
| work_keys_str_mv | AT fernandezricoc colloidalsu8rodsandbananashapedparticlessynthesisandliquidcrystalselfassembly |