Nuclear magnetic resonance and rheological studies of carbohydrate-1-ethyl-3-methyl-imidazolium acetate solutions

• Main Author: Ezzawam, Wafa Mosbah
• Other Authors: Ries, Michael
• Published: University of Leeds 2018
• Subjects: 500
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.758328

The dissolution of carbohydrates in Ionic liquids has received attention for many decades and still is to this day. Solutions of xylan and xylose in 1-ethyl-3-methylimidazolium acetate [C2mim] [OAc] were individually examined at various temperatures (20 °C-70 °C) using NMR spectroscopy, diffusion and the low field spin-lattice and spin-spin relaxation times (T1 and T2) as well as rheology measurements. The ratio of the diffusion coefficients for the anion to the cation remained constant upon the addition of xylan and xylose, showing that the anion and cation were equally affected by the presence of the carbohydrate. The activation energies for translational diffusion motion of both ions in the xylose solutions were similar to these found in published cellobiose. The addition of xylose and xylan individually have affected the mobility of the protons, with a decrease occurring with increasing carbohydrate concentrations. We are looking at the interactions between plant polymers, such as xylan with cellulose, with the aim to form biomimetic materials. A solution of cellulose and xylan in the ionic liquid 1-ethyl-3-methylimidazolium acetate [C2mim] [OAc] was examined using NMR diffusion, low field relaxometry and rheology measurements at various temperatures (20 °C-60 °C). We observed that the dissolving mechanism of xylan in the IL [C2mim] [OAc] is close to that for cellulose. The diffusion coefficient of the anion is preferentially more reduced by cellulose than by xylan. It is generally agreed that the anion is more active in the dissolution of carbohydrates than the cation. The dissolution mechanism of cellulose and xylan in the IL [C2mim] [OAc] can be examined via the mobility of the ions. We proposed that the number of accessible OH groups belonging to the carbohydrates are reduced at certain xylan-cellulose blend compositions, showing that at these concentrations there are significant interactions between the two biopolymers.