Characterization and Kinetics of Microheterogenities in Ionic Liquids

• Applicant: Dr. Bernd Rathke
• Subject Area: Technical Thermodynamics
• Term: from 2008 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 90929230

Structure and dynamics of Ionic Liquids will be investigated on a mesoscopic scale by static and dynamic light scattering at ambient pressure and at high-pressure conditions up to 700 bar in a temperature range of 0 - 150 °C.Studies on the microstructure in binary solutions of Ionic Liquids at ambient pressure indicate the evidence of equilibrium and non-equilibrium inhomogeneities with sizes on the nanometer and the micrometer scales and typical decay times in the order of some hours up to several days. Because the scattering behavior in binary systems can be substantially influenced by critical fluctuations this work is focused on long-range correlations in pure ionic liquids, particularly in 1-alkyl-3-methylimidazolium (bistrifluoromethylsulfonyl)imides. Computer simulations and x-ray diffraction experiments have indicated the presence of ordered domains also in pure ionic liquids. By using light-scattering we extend the experimental attainable window and draw attention to processes on the mesoscopic scale while x-ray and neutron based techniques as well as computer simulations are limited to smaller length-scales and shorter time-scales.In order to clarify questions about the stability of long-range inhomogeneities we will perform additional kinetic investigations by disturbing equilibrated samples by rapid pressure changes. The scattered light as well as the pressure change is recorded and analyzed with suitable time resolution. With our technique we are covering characteristic times of structural changes in the system in the range of 10-3 s up to 105 s.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1191: Ionic Liquids
• Participating Person: Professor Dr. Wolfram Schröer