Self-assembly in deep eutectic solvents

Abstract

Deep eutectic solvents are environmentally sustainable liquids obtained through the combination of simple, readily available precursors. Their chemical diversity comes about from the myriad possible combination of precursors, leading to the development of solvents with suitable characteristics for particular applications. Unlike traditional covalent solvents, deep eutectic solvents present an intrinsically complex molecular network, with both hydrogen bond and electrostatic contributions balancing the stability of the mixture. Thus, these solvents may be considered as a non-aqueous environment where traditional processes can be mimicked, but with a greater control over the system properties.Self-assembly of amphiphiles has become a highly relevant field for science and technology, with present and future applications in templating of nanostructured materials, drug delivery, formulations and detergency, among others. The aim of this project is to develop a suitable framework that describes amphiphile self-assembly in deep eutectic solvents. As a starting point, an investigation of surfactant aggregation was performed, combining in-house techniques, such as surface tension and calorimetry, with cutting- edge X-ray and neutron scattering techniques: small-angle scattering and reflectivity. The results show the formation of micelles for which, through electrostatic interactions between the solvent and the amphiphiles, the morphology can be tuned.The characteristics of deep eutectic solvents have also attracted the attention of the biochemistry community, pursuing development of these solvents as alternatives to water in bio-sensing devices, for enzymatic reactions, and for preservation of bio-active compounds. Therefore the investigation was extended to include the behaviour of phospholipids and proteins. The formation of stable phospholipid monolayers demonstrated deep eutectic solvents to be, to date and best of my knowledge, the only non-aqueous solvent that supports such behaviour. Also, the conformation of proteins has been investigated, showing the partial or total folding of proteins in pure and hydrated deep eutectic solvents.The work includes several individual systematic investigations that merge in this thesis. From the basic understanding of surfactant behaviour to the preliminary investigations in the physicochemical characteristics of biomolecules in deep eutectic solvents, these studies were combined to in a pioneering investigation in this field. It is hoped that these results and ideas will lead to new applications and more efficient technologies, and ultimately contribute to the development of a better world.

Date of Award	15 May 2018
Original language	English
Awarding Institution	University of Bath
Sponsors	European Spallation Source
Supervisor	Karen Edler (Supervisor) & Andrew J. Jackson (Supervisor)