Chapter 3: Diffusion and Relaxometry to Study Carbohydrates Dissolved in Ionic Liquids

Solutions of xylan and xylose in 1-ethyl-3-methylimidazolium acetate [C2mim] [OAc], a room temperature ionic liquid, were examined across a range of temperatures (20°C–70 °C) using: NMR spectroscopy; diffusion; low-field (20 MHz) spin–lattice and spin–spin relaxation times; and rheological measurements through the zero shear rate viscosity. The addition of xylose and xylan affect the mobility of the ions, with a decrease occurring when the carbohydrate concentration is increased. The ratio of the diffusion coefficients for the anion to the cation remained constant upon the addition of both xylan and xylose, showing that the anion and cation were equally affected by the presence of the carbohydrate. The translational diffusion motion of the ions in the xylose solutions were similar in value to published results for cellobiose, which we explain in terms of the number of available carbohydrate OH groups that the ions are interacting with. We observe from the various NMR results that the dissolving mechanism of xylan in [C2mim] [OAc] is similar to that for cellulose.