In this project supported by the Experimental Physical Chemistry Program, Professor Guillermo Moyna at the University of the Sciences in Philadelphia and his group will employ nuclear magnetic resonance (NMR) methods to probe the structure and dynamics of a series of 1-alkyl-3-methylimidazolium based ionic liquids (ILs) and solutions containing these ILs, cosolvents of different polarities, and various carbohydrates. Specifically, deuterium isotope effects on chemical shifts, relaxation measurements, and diffusion determinations will reveal the connection between molecular level interactions and such properties as viscosity, and the ability of certain ILs to dissolve other species such as carbohydrates derived from biomass. Molecular dynamics simulations will be performed to complement the experimental studies and develop atomistic models of these systems.
In addition to gaining a better understanding of the basic science of IL-based systems and IL-mediated processes, achieving the project objectives will impact a broad swath of disciplines. For example, the data from these studies may aid in the design of new IL-based media that could find direct application in fields ranging from water remediation to biomass processing. In addition, the project will engage students at various levels of their careers in both experiment and theory. This will allow senior members of the research team to hone their skills as teachers and mentors, while at the same time providing the younger investigators in the group with the unique opportunity of learning advanced chemical concepts by doing chemistry.
The project "Structure, Solvation, and Dynamics in Ionic Liquids" involved the study of a number of aspects of ionic liquids (ILs), novel materials with enormous "green" potential that can be used in a wide number of industrial processes as replacements of traditional, and oftentimes toxic and/or poluting, solvents. In particular, our work focused on the ability of ILs to dissolve natural polymers present in biomass which are insoluble in water and other common solvents. Among these polymers is cellulose, the most abundant component of wood. Part of our studies focused on elucidating the mechanism by which ILs can efficiently dissolve these polymers. The properties of ILs are determined by how their component ions interact, and they are also profoundly influenced by the precense of water and other substances. We therefore designed and carried out a number of experiments to investigate these phenomena as well. Our results provided important insights in all these areas. First, using both nuclear magnetic resonance (NMR) experiments and computer-based molecular dynamics (MD) simulations, we were able to determine that the ability of ILs to dissolve cellulose depends mainly in the nature of its negatively-charged fragment, or anion. Employing similar methods we were able to show how some solvents, such as water and alcohols, disrupt the structure of ILs and reduce their capacity of dissolve biopolymers, and that others, such as dimethylsulfoxide, are unable to interfere with these interactions and act as additives. Using isotope effect measurements we were also able to detect weak interionic hydrogen bonds, forces that could have an important role in the structure and properties of these materials. In addition to publications in peer-reviewed journals and presentations at schoolarly meetings, the project engaged post-doctoral and undergraduate students in experimental and theoretical research. This allowed senior members of the research team to hone their skills as teachers and mentors, while at the same time providing the younger investigators with the unique opportunity of learning advanced chemical concepts by doing chemistry. Such interactions are critical to the formation of future science scholars and researchers.