Structure, Dynamics, and Self-assembly in Ionic Liquids

Abstract

Ionic liquids (ILs) are a novel class of new liquids completely made of ions. They often exhibit low vapour pressure and tuneable solvent properties which are desired by many applications and industries. However, their current applications are mostly identified by trial and error. Gaps in our fundamental understanding inhibit the rational design and optimisation of these solvent systems. A large part of ongoing IL research is aiming to fill this gap and to understand the structure-property relationships of these liquids. This is also part of a broader scientific endeavour of making modern solution processes more efficient and sustainable by replacing harmful organic solvents with more efficient or biofriendly ILs. This thesis simultaneously focuses on three aspects of ILs. Firstly, we have studied the molecular arrangement in ILs to understand the origin of liquid structure and how it can be tuned by ion design or additives. Then we investigated the time-dependent aspects of liquid structures that potentially underpin their transportation properties. Finally, to bridge our understanding and the bulk behaviour of ILs as functional solvents, we have examined some model systems involving the self-assembly of surfactants and lipids. We were able to reveal unexpected origins of liquid structures, capture dynamics that associate with the loss of memory of polarity networks, and explain unusual self-assembly behaviours in ILs. Throughout, we have demonstrated that ILs are truly designer solvents with many tuneable features, and we have provided new insights into their design rules