Structure and Dynamics of Mixtures of Ionic Liquids and Polyethers

Ionic liquids are salts that remain liquid near ambient temperatures. Characteristics such as extremely low vapor pressure and excellent thermal stability have led them to receive significant attention as potential solvents for separation processes and a plethora of other applications. One drawback of ionic liquids, however, is that they tend to be more viscous than conventional solvents. The large viscosity may be a limiting factor for the use of ionic liquids in industrial operations due to high mass transfer resistance and increased pumping and handling costs. One strategy being used to reduce the viscosity of ionic liquids is to mix them with small amounts of low viscosity additives such as polyethers or other low volatility fluids. 

In order to understand the role additives have on the structure and dynamics of ionic liquids, we have carried out extensive molecular dynamics simulations on mixtures containing imidazolium-based ionic liquids and polyethers. Viscosities, self-diffusivities and rotational dynamics were computed as a function of polyether concentration and temperature. Structural properties such as radial and spatial distribution functions and end-to-end vectors were computed and used to help understand the trends in the dynamics. Comparison with available experimental data shows that the simulations are able to accurately capture both pure fluid and mixture dynamics.