Probing the change in the structure of an ionic liquid upon a liquid-liquid transition

Crystalline solids are characterised by high ordering at a microscopic level, forming a crystal lattice. It is common for a crystalline material to occur at different crystalline forms, with different lattices (polymorphism). In liquids, molecules are disordered, albeit strongly interacting, and are able to move freely with respect to one another. Although some elements and metal oxides have more than one liquid structure, displaying high-temperature liquid-liquid transitions (LLTs), only a handful of room-temperature liquids display LLTs. Recently, an entire family of ionic liquids (salts that are liquid around room temperature) have been reported to display LLTs below ambient temperature. This study aims to uncover, for the first time, how molecules of ionic liquids rearrange themselves upon such transition, and how this phenomenon could be used to design new functional liquids.