Mac Fhionnlaoich, Niamh;
(2021)
Stimuli Responsive Liquid Crystal-Nanoparticle Composites.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Composites of liquid crystals and nanoparticles offer unique properties for applications including displays, sensors, plasmonics and metamaterials. Their potential is two-fold: the anisotropic and ordered nature of liquid crystals provides a promising medium in which to control characteristics and direct self-assembly of nanoparticles; likewise, inclusions of nanoparticles tune attributes of liquid crystals, such as the ordering and optical properties. In this work, the thermotropic liquid crystal, 4-cyano-4’-pentylbiphenyl, acted as a complex medium for the manipulation of functionalised gold nanoparticles. The research presented herein follows three streams. First, to develop a deep understanding of the materials used, novel methodologies were developed. The nanoparticle entropy provides an assumption-free measurement of dispersity for nanoparticle populations. Furthermore, a spatial distribution function was constructed for the 2D evaluation of colloidal ordering that highlights structure, periodicity, and anisotropic ordering. Software was produced for both techniques and made freely available. Second, the synthesis and functionalisation of gold nanoparticles was studied and optimised to promote miscibility in the liquid crystal. A design of experiments-based approach was implemented to develop an understanding of key experimental conditions and interactions during synthesis and functionalisation. Third, the effects of various stimuli on the liquid crystal mediated self-assembly of gold nanoparticles were investigated. The isotropic to nematic phase transition was leveraged to form reversible arrays of nanoparticle aggregates with tuneable size and interaggregate spacing. Furthermore, procedures for the induction of concentration gradients of nanoparticles in the composite material were established through exposure to light and heat. Overall, this work provides a framework for the reliable preparation of highly soluble gold nanoparticles in complex media as well as novel insights on stimuli-responsive liquid crystal-nanoparticle composites with respect to temperature and light. Finally, both accompanying methodologies, i.e. the nanoparticle entropy and spatial distribution function, can be applied to a wider range of scientific problems.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Stimuli Responsive Liquid Crystal-Nanoparticle Composites |
| Event: | UCL (University College London) |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| Keywords: | Liquid Crystals, Nanoparticles, Liquid Crystal-Nanoparticle Composites, Soft Matter, Design of Experiments |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10137494 |
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