- Title
- Nanostructure of ionic fluid systems
- Creator
- McDonald, Samila
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2018
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Structure underlies many important processes in biology, chemistry and physics. At the liquid-solid interface, the behaviour and arrangement of liquid molecules (neutral or charged) underpins electrochemical battery performance, tribological performance of lubricants, and determines stability in colloidal particle or polymer systems. Ionic fluids are emerging as a promising class of solvents for the above applications, but are limited by the lack of knowledge surrounding their structure at solid interfaces with added ionic solutes. This thesis uses amplitude modulated atomic force microscopy (AM-AFM) to reveal nanometre resolution of adsorbed ions from complex fluid systems at atomically smooth surfaces, mica and highly ordered pyrolytic graphite (HOPG). The adsorbed layer, also known as Stern layer or electrical double layer (EDL), is ordered and templated by the surface nanostructure. Adding ionic solutes changes the solvent nanostructure significantly, even at low concentrations. This thesis extends current research in the field of AM-AFM and solid-liquid interfaces by providing new evidence for ion adsorption, which can be used to infer how electrochemical devices are impacted by ionic additives. Studying poly(ethylene oxide) (PEO) solutions in non-aqueous solvents is a large field in polymer electrolyte (PE) development. Ionic fluids are potentially suitable solvents for PEO, and can act as the electrolyte for charge transfer. However, the conformation of PEO, which is linked to PEO solvent quality and solvation, is poorly understood. This thesis uses small angle neutron scattering (SANS) to elucidate the polymer solvent quality of poly(ethylene oxide) (PEO) in a range of solvate ionic liquids and deep eutectic solvents. While the PEO conformation is similar in all fluids studied, the technique is sensitive to changes in fluid composition (the change in ion structure and shape), which provides fundamental understanding of intermolecular interactions between the ionic solvent and PEO. Such information contributes to current research in improving and designing ionic fluid systems for a variety of applications. Deep eutectic solvents (DESs) are a developing ionic fluid composed of solid salts and hydrogen bonding donor molecules that form low-melting mixtures at the eutectic point and exhibit favourable properties. It has been shown that amphiphilic protic ionic liquids (PILs) are nanostructured in the bulk, and that dissolved inorganic salts and small molecule solvents can influence bulk nanostructure. PIL nanostructure results from attractive solvophobic interactions between amphiphilic cation alkyl chains, and becomes better defined as the cation alkyl chain length is increased. This thesis synthesises a class of amphiphilic deep eutectic solvents (DESs) with ion structures derived from amphiphilic PILs. This thesis will elucidate the nanostructure of 1:2 molar ratio mixtures of ethylammonium bromide (EABr) and butylammonium bromide (BABr) with glycerol to reveal the effect of cation alkyl chain length on nanostructure in these DESs. Overall this thesis contributes significantly to understanding ionic fluid systems and how their nanostructure is affected by solute addition.
- Subject
- small angle neutron scattering; deep eutectic solvents; PEO conformation; ionic fluids; ionic fluid systems
- Identifier
- http://hdl.handle.net/1959.13/1395657
- Identifier
- uon:33919
- Rights
- Copyright 2018 Samila McDonald
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 11 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 314 KB | Adobe Acrobat PDF | View Details Download |