Ionic liquids (ILs) are substances composed exclusively of ions that are liquid below 373 K. Room temperature ionic liquids (RTILs) are like ILs but they are also liquid at 298 K. ILs have recently become of interest as a replacement for volatile organic solvents as they generally have little or no vapour pressure and high thermal stabilities meaning that they are more easily contained than traditional solvents. ILs are also of interest in electrochemistry because they can possess large electrochemical windows (EWs) when compared to conventional solvents. This study reports the synthesis of a library of tetraalkylammonium halide salts.

Supported ionic liquid phase catalysis is a thriving area of research with many applications. Currently, investigations in this area have focussed on the applications of these systems and there are relatively few reports on the understanding of the interactions of the ionic liquid with the porous support. The aim of this research is observe and analyse these interactions for a number of model systems. The supported ionic liquid phases (SILPs) discussed herein are made up of an ionic liquid physisorbed onto a mesoporous silica host. The ionic liquids used were chosen because of their ease of handling and similarity in structure. Mesoporous silicas were chosen due to their tunable properties. The potential applications of the systems described here in range from catalysis to gas processing and storage. As the focus of this research is characterisation of the interactions between the ionic liquid and the porous silica support, storage of CO2 gas is the . only application explored herein. NMR spectroscopy has been extensively used in this research. Not only has it been a versatile tool for elucidation of structures, it has also allowed the measurement of changes in the dynamics of the ionic liquid upon encapsulation. Combination of high resolution and solid state NMR spectroscopy has also been used to identify the presence of gases in clathrate hydrates. A semi-clathrate hydrate was loaded with methane gas. Solid state NMR experiments were then used to indentify methane molecules present in the cages of the clathrate and quantify the percentage uptake with respect to the semi-clathrate hydrate host.

The Petronas C02 project aimed to design an ionic liquid-based technology for the removal of C02 from natural gas. Current technology using amine-based system is not economical. It is envisioned that an ionic liquid method has the potential to be superior to current technology, due to their unique characteristics, such as high thermal stability, negligible vapour pressure and the possibility to fine-tune their properties, by combining appropriate cations and anions. This project involved the development of a "simple" synthetic method for ionic liquids, utilising Group 2 metal hydroxides (especially, strontium hydroxide octahydrate). This gave a wide array of carboxylate ionic liquids, via an intermediate hydroxide solution. It is a very simple, straightforward procedure which uses starting materials which are commercially available in bulk. The classes of carboxylate ionic liquids that have been synthesised and fully characterised are those based on the cations: l-ethyl-3-methylimidazolium, tributylmethylammonium, tetraalkylphosphonium and l -al kyl -l-methylpyrrolidinium. The Hunig's based derivatives of l -alkyl•3•methylimidazolium bistriflamides, as well as phosphonium and ammonium caboxylates were tested for their ability ty to absorb C02. In the anhydrous us system, initial screening showed that the most promising anions for C02 solubility are the methanoate and ethanoate. In parallel, it was observed that the C02 solubility in ionic liquids was not greaby the alkyl chain length on cation. The most noticeable effect on C02 capture was the addition of 1 mole of water to the carboxylate ionic liquids. This greatly enhanced the solubility of C02 by an order of magnitude, which is due to a different mechanism of C02 absorption; chemisorption on in the presence of water, instead of physisorption. A mechanism via the formation of hydrogencarbonate has been proposed due to this remarkable ability for C02 capture, which was later proven by other team members. All in all, the system that has been put forward for consideration as a potential C02 absorber in industrial processes within Petronas is the equimolar system of [4441][CH3C02] and water .

The search for bioactive compounds from natural sources has been on-going for centuries. The synthesis and/or isolation of these valuable compounds make them reasonably expensive; in addition their production is often wasteful given the quantities of volatile organic compounds (VOCs) often used. In recent years research in ionic liquids (ILs) and biomass dissolution has increased due to the ' beauty' of this relatively novel solvent to effectively break down the hard matrix of difficult biopolymers. This positive step in biomass dissolution offers the possibility of completely separating lignocellulosic biomass into its major polymeric components: cellulose, lignin and hemicelluloses. We can therefore apply this knowledge to the extraction of bioactive compounds ,from biomass. Herein two types of biomass were considered; land biomass (cinnamon bark) and aquatic biomass (macroalgae). This project involved two major phases. Firstly, evaluating the effect of IL pre-treatment of these types of biomass against conventional methods such as autoclave extraction, Soxhlet extraction, hot and cold maceration, hydrodistillation and supercritical carbon dioxide extraction. These methods were compared in terms' of the percentage yields of. the extract recovered and their overall feasibility. As this project specifically targeted higher value materials particularly .from macroalgae another major part of this project was the development of an experimental protocol for the evaluation of the biological activity of extracts recovered from the brown algae. The tests chosen were the antioxidant and anti-diabetic properties and again were evaluated after the protocols were developed. These tests were chosen for their growing importance to society. , It has been shown that the extracts recovered from the ionic liquid & solution were higher than that from the conventional methods employed. Nevertheless the extracts from the conventional methods had higher biological activity than those from the ionic liquid. Ionic liquid contamination and recovery of pure materials was also complicated due to the nature of ionic liquids.

Protic ionic liquids (PILs) are a vast class of compounds that are expected to play an increasing role as fuel cell electrolytes. A crucial aspect of these systems is represented by the reversible proton transfer reaction between a Bronsted acid and a Bronsted base giving rise to the ionic phase out of a molecular neutral state. Thermodynamic, structural and chemical properties of a prototypical PIL, ethylammonium nitrate (EAN), have been investigated by a combination of different computational approaches, ranging from ab initio to classical simulations based on a reactive Monte Carlo algorithm. Ab initio methods have been applied to map the potential energy surface and reaction energies of EAN-related molecules and small clusters. Crystal structures and vibrational properties of small clusters have also been investigated at the ab initio level. The ab initio data have been used to parametrise a reactive force field, able to reproduce the acid-base equilibrium of EAN, and which has subsequently been used to carry out a detailed investigation of the hydrogen bond network in liquid EAN, using the size of the hydrogen atom as a free parameter to explore a wide variety of conditions ranging from weak to strong hydrogen bonding. Equilibrium properties such as the crystal and liquid density are well reproduced by the model which provides only a rather crude description of fluidity and cohesive energy. In addition, Monte Carlo simulations have been carried out to investigate the properties of small EAN clusters in equilibrium with their vapour. The results show a complex pattern I of ionic and neutral molecular phases as a function of cluster size and thermodynamic conditions. As a side investigation, a simulation study of electrowetting and liquid-vapour nucleation for the restricted primitive model was carried out in order to clarify crucial aspects of Coulomb systems.

This thesis contains work primarily pertaining to two different projects, with the majority of work carried out at Queen's University of Belfast, QUS, along with some at TUDelft, Delft University of Technology, Delft, NL. The first project was concerned with the development, optimisation, and implementation of high throughput inexpensive, and facile toxicity testing methods for use with novel ionic liquids. Approximately one hundred ionic liquids were tested against two strains of bacteria - one Gram negative and one Gram positive. The results varied from no-to-low inhibit ion zones to large inhibition zones, indicating toxicity to the organisms tested. The second project was concerned with the use of ionic liquids as co-solvents in a biocatalytic reaction involving novel enoate reductase enzymes. Approximately twenty ionic liquids, both water-miscible and water-immiscible were tested. Two methods were used for the analysis of the reactions performed, ultraviolet spectrophotometric analysis and liquid -liquid extraction combined with gas chromatographic analysis. The water-immiscible ionic liquids garnered better results when tested with the enzymes of interest than did the water-miscible ones.

This Thesis explores the subject of the characterisation and properties of the vapour phase of ionic liquids (ILs). Chapter 1 provides a review of the relevant literature and a general introduction to the field. Chapter 2 gives a review of the primary technique used to record the results presented in this Thesis, temperature programmed desorption (TPD). The review also encompasses a description of line of sight mass spectrometry (LOSMS), the technique used for monitoring IL desorption at ultra-high vacuum (UHV).

The main goal of the project has been to develop a better microscopic description of electrostatic interactions in colloidal systems. We have developed a variational field theory that consistently incorporates ion-ion correlation effects, dispersion interactions, and image charge interactions. This theory has been applied to investigate the influence of electrolytes on the interaction between colloidal particles at low to moderate electrolyte concentrations. The theory has also been modified to study coulomb systems in the strong coupling regime. This theory has been applied to study the interaction between charged surfaces with neutralizing counterions and salt, with good agreement between theory and simulation. We have also studied specific-ion effects, such as the Hofmeister series, which has been a long standing problem in chemistry and biology. In particular, we have included ion polarizability in the theory and studied the double layer interaction at the mean field level.

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This thesis describes the compositional limits, phase stability and electrical properties of several oxide ion conducting phases in the Bi₂O₃-V₂O₅ binary and Bi₂O₃-V₂O₅-Na₂O ternary phase diagrams.  Samples were prepared either by the mixed oxide route frm Bi₂O₃, V₂O₅, and Na₂CO₃ reagents or by hydrothermal processing of Bi₂O₃ and V₂O₅ using (2-3 M) NaOH.  Sample were analysed using a combination of techniques including x-ray (XRD) and electron diffraction (ED), thermal analysis (DTA/TGA), electron probe micro-probe analysis (EPMA), and impedance spectroscopy (IS). The well-known oxide ion conductor, based on the ideal composition Bi₄:V = 2:1) was shown to exist as a solid solution phase between 2.15:1 = 2.5:1 at 800 - 850°C.  XRD, ED, and EPMA data provide evidence for a new polymorph (<span style='font-family:Symbol'>d) for Bi-rich compositions based on a defect fluorite <span style='font-family:Symbol'>d-Bi₂O₃ cell, in addition to the well-known <span style='font-family:Symbol'>a, <span style='font-family:Symbol'>b, and <span style='font-family:Symbol'>g polymorphs.  This solid solution exhibits the highest level of oxide ion conductivity (at 800°C) of all the phases studied, with values of <span style='font-family:Symbol'>~ 0.1 Scm^-1 at 800°C.  Post-annealing samples at 650°C for extended periods show that the Bi-rich solid limit is strongly temperature-dependent and hat compositions 2.4-2.5:1 are metastable and decompose into phase mixtures which include a low temperature triclinic phase based on a face-centred cubic cell with composition Bi_2.9VO_6.85. The next solid solution phase occurs at 3.5-3.75:1 and not at 4:1 as has been previously believed.  Selected area electron diffraction (SAED) revealed complex crystal chemistry with the existence of three different types of patterns all based on a 3-fold multiple of a <span style='font-family:Symbol'>d-Bi₂O₃ fluorite-type subcell.  Most crystals had incommensurate modulation and also streaking indicative of structural disorder, attributed to variations in the stacking order of V₄O₁₀ units within the cell. Samples were stable after post-annealing at lower temperatures, suggesting they are thermodynamically stable, albeit with complex, low crystal symmetry.  They are modest oxygen ion conductors with <span style='font-family:Symbol'>s-5 mScm^-1 at 800°C.