Effect of Dissolved Cellulose on Molar Conductivity and Dynamic Viscosity of 1-Ethyl-3-Methylimidazolium Acetate Solutions

Wednesday, 4 October 2017: 16:40
Chesapeake G (Gaylord National Resort and Convention Center)
P. J. Fahey (Department of Chemistry, U. S. Naval Academy), E. T. Fox (Department of Chemistry, U.S. Naval Academy), M. Gobet, S. Greenbaum (Department of Physics and Astronomy, Hunter College, CUNY), H. C. De Long (Physical Sciences Directorate, U.S. Army Research Office), and P. C. Trulove (Department of Chemistry, U. S. Naval Academy)
This study determined the effect of dissolved cellulose on the ion conductivity, dynamic viscosity, and density of 1-ethyl-3-methylimidazolium acetate (EMIAc). Cellulose solutions were prepared with three different solvents and two different sources of cellulose. The solvents were pure EMIAc, EMIAc combined in a 1:1 mole ratio with water, and EMIAc combined in a 1:1 mole ratio with acetonitrile. The cellulose sources were microcrystalline cellulose (MCC) and cotton. MCC was tested at 0, 0.001, 0.005, 0.01, and 0.03 g (g solution)-1 and cotton was tested at 0, 0.001, 0.005, and 0.01 g (g solution)-1. Each solution was evaluated over the range of 20 to 60°C. Both MCC and cotton increased the dynamic viscosity and decreased molar conductivity (with several small exceptions) for all three solvent types. The fractional changes (from zero cellulose content) for dynamic viscosity were large compared to the fractional changes in molar conductivity. The source of cellulose had a large impact on the resulting change in dynamic viscosity, as cotton increased dynamic viscosity drastically more than MCC for a given cellulose mass fraction for all solvents. For comparison, solutions were also made with glucose and cellobiose instead of cellulose in order to remove the inherent movement constraints on anhydroglucopyranose moieties within the cellulose chain. These comparisons help to understand why the addition of cellulose polymer affects dynamic viscosity more than molar conductivity by one or more orders of magnitude. Knowledge of the ion transport phenomena will allow a more thorough understanding of why ionic liquids like EMIAc are capable of dissolving biopolymers like cellulose.