FWF P19807: Simulation studies of ionic liquids
|grant holder||Prof. O. Steinhauser|
|funding period||06/2007 - 05/2012|
|project sum||277 k €|
AbstractIonic liquids (IL) offer a variety of physical properties that make them attractive replacements for traditional organic solvents. Because of their non-volatility, ILs have gained increased attention as ''Green Chemistry'' solvents in the past decade. Most of them are moisture-stable thus offering the opportunity to use IL/water mixtures as novel solvents. By varying the molar ratio of IL vs. water, the role of ILs as solvents/co-solvents can be studied systematically. Due to strong electrostatic interactions, pure ILs may be seen as an ionic network. Therefore, IL/water mixtures are characterized by the co-existence and competition of a hydrogen-bond and an ionic network. First experimental results for these fascinating binary networks exist, but systematic computer simulation studies have not been reported yet. Therefore, we plan intensive investigations of ILs as solvents/co-solvents by molecular dynamics simulation. Collective properties, such as viscosity, conductivity and dielectric constant provide a quantitative measure of the cooperativity of the underlying ionic/hydrogen bond networks. For example, the tight coupling of ion pairs results in a low static conductivity in pure ILs. In mixtures with water, however, the competition with and integration into the hydrogen bond network weakens ionic pairs and thus enhances the conductivity as well as it reduces the viscosity. In addition, the higher polarity of the additional water component leads to a dielectric increment. The potential of ILs (pure or in mixtures with water) as novel, benign solvents offers interesting applications in biomolecular solvation. This part of the project will be the most challenging one, because now three networks, the IL ionic network, the water hydrogen bond network and the internal network of the biomolecular solute co-exist and compete. The simulation and interpretation of such a complex triple network goes beyond current routine computational studies. We will follow a stepwise approach involving smaller biomolecular solutes. In detail, we will analyze three major aspects: (i) The structure and stability of the hydrogen bond network of the biomolecular solute, (ii) the structure of the solvent/co-solvent in the vicinity of the solute (iii) the dynamics of the solvent/co-solvent molecules, in particular their retardation as compared to the bulk. Altogether, the computational analysis of the collective behavior of ILs requires extremely good statistics. Thus, the simulation period to be covered has to be approximately 20 times longer than that of state of the art simulations.
- Prof. H. Weingärtner (University of Bochum)
|Imprint:||(as stipulated by Austrian law, MedienG 2005): S. Boresch / C. Schröder,|
|Institut für Computergestützte Biologische Chemie, Währinger Strasse 17, 1090 Wien, Austria|