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Title: A computational investigation of local interactions within ionic liquids and ionic liquid analogues
Author: Ashworth, Claire
ISNI:       0000 0004 7228 3636
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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The potential applications of ionic liquids and related analogues are diverse. However, for large-scale industrial applications low cost ionic liquids are required. Moreover, for the full potential of ionic liquids to be realised, a fundamental link between molecular level interactions, structuring and the bulk phase properties must be established. Deep eutectic solvents (DESs) and protic ionic liquids have been identified as candidates for the potential application of chalcopyrite leaching. The choline chloride – urea DES and 1- butylimidazolium hydrogensulphate protic ionic liquid were selected as systems of primary interest. Local structuring within the selected systems has been investigated, with an emphasis on the hydrogen bonding interactions. The choline chloride – urea mixture is a prototypical example of a DES. Using DFT, the pairwise interactions between the constituent components, and within clusters composed of n.urea.choline-chloride (n = 1-3), have been evaluated. Many different types of hydrogen bond have been identified, exhibiting flexibility in both strength and number. The formation of the commonly proposed [2urea⋅Cl]– complexed anion has been scrutinised and found to be energetically competitive with other interactions. Moreover, contrary to existing proposals, the negative charge is found to remain localised on chloride. The cation-anion and anion-anion interactions within [C4Him][HSO4] and related systems have been compared and contrasted;; ion pairs were evaluated using DFT and the bulk systems modelled using classical MD. Local structuring within [C4Him][HSO4] exhibits features of both the aprotic analogue and alkylammonium protic ionic liquids. [HSO4]–⋅⋅⋅[HSO4]– interactions have been considered and found to be a notable feature of the [HSO4]– ionic liquids studied. It is anticipated that the formation of [HSO4]– aggregates influences the properties of the bulk systems. A QM/MM method for the study of ionic liquids is introduced. Preliminary analysis suggests that this is a viable approach for the investigation of local structuring within ionic liquids.
Supervisor: Hunt, Patricia Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral