Nanoscale Heterogeneity and Dynamics of Room Temperature Ionic Liquids

Research Summary: An increase of the alkyl chain length of the cation of room temperature ionic liquids (RTILs) influences the nanoscale structure and dynamics of RTILs, which in turn affect the behavior of RTILs at solid-liquid interfaces central to energy storage devices. We integrate classical molecular dynamics (CMD) simulation, fluorescence correlation spectroscopy (FCS), time resolved fluorescence anisotropy decay (TRFAD,) small angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR) to investigate the fundamental properties including structure, dynamics and interfacial behavior of RTIL electrolytes. We found that the elongation of the alkyl chain in the cation gives rise to an enhanced spatial and dynamical heterogeneity, which have been observed in CMD, FCS, TRFAD and SAXS; CMD combined with NMR has revealed the weak temperature dependence of the dynamics of RTILs at a silica surface due to the surface roughness and strong interaction between the ions and silica walls.