Kinetics of Water-Mediated Fluctuations in Room Temperature Ionic Liquid: N, N-Diethyl-N-methyl-N-(2-methoxyethyl) Ammonium Tetrafluoroborate

The kinetics of small-angle X-ray scattering (SAXS) was assessed in the room temperature ionic liquid (RTIL)–x mol% H2O system, where the RTIL is N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate, [DEME][BF4]. During equilibration of a non-equilibrium state, the largest time evolution of SAXS was observed at approximately 90 mol% H2O. Above 85 mol% (xc), the SAXS intensity increased gradually for 24 h. For the larger q region, the prepeak and principal peak in X-ray diffraction patterns have no time dependence in the water-rich region (70–91 mol%). The long time relaxation process observed in SAXS was related to the outstanding pH oscillations at 90–95 mol% over several days in the [DEME][BF4]–water system. The xc for nonequilibrium anomalies is related to the equilibrated crossover concentration from 65–85 mol% (from SAXS) to 85–95 mol% (for the prepeak in X-ray diffraction) in the [DEME][BF4]–H2O system. Inside [DEME][BF4], the dynamic and static properties of hydrogen bonding of water changed drastically at xc.