Research Fellows Directory
Dr Michael Ries
University of Leeds
Cellulose is one of the greatest achievements of evolution. [Cellulose (2012) 19:589–598] Polysaccharides such as cellulose are polar, hydroxylated and hydrophilic making them invaluable to Nature. Life uses these molecules to build materials of high strength, store energy and manage moisture. The strength building features of cellulose stem from its crystalline morphology that enables the transfer of stress from one molecule to another. But the very forces that hold these structures together, giving cellulose its outstanding material properties, are the very forces that stop its dissolution. Without being able to dissolve cellulose we cannot unlock its true potential as a practically inexhaustible source of renewable raw material, to reduce our dependency on conventional fossil fuel based plastics.
In 2002 a pioneering study showed that it was possible to dissolve cellulose in an ionic liquid and subsequently form materials of pure cellulose by coagulation through the addition of water that triggers the cellulose to clump together and fall out of solution. An ionic liquid is a salt that at room temperature is in the liquid state and so flows like water even though there is no water present. These ionic liquids have very powerful dissolving capabilities and almost no vapour pressure giving them the name “green” solvents. On top of this there are countless combinations of cations and anions to form ionic liquids from making them “designer” green solvents.
The resultant properties of the coagulated cellulose are dependent on the quality of the solvent and the rate of induced coagulation. These factors affect the morphology, which can range from a dense glassy material to a network of interconnected pores. The potential end use of the cellulose as a membrane, fibre or film is dependent on having the correct morphology. This project concerns understanding and exploring the relationships between solvent properties, coagulation kinetic and resultant material properties.