From Ionic Liquid to Electrolyte Solution: Dynamics of 1-N-Butyl-3-N-methylimidazolium Tetrafluoroborate/Dichloromethane Mixtures

Dielectric spectra have been measured at 25 degrees C for mixtures of the room temperature ionic liquid 1-N-butyl-3-N-methylimidazolium tetrafluoroborate (IL) with dichloromethane (DCM) over the entire composition range at frequencies 0.2 less than or similar to v/GHz <= 89. The spectra could be satisfactorily fitted by assuming only two relaxation modes: a Cole-Cole process at lower frequencies and a Debye process at higher frequencies. However, detailed analysis indicated that both spectral features contain additional modes, which could not be resolved due to overlaps. The spectra indicate that the IL appears to retain its chemical character to extraordinarily high levels of dilution (X-IL greater than or similar to 0.5) in DCM. At even higher dilutions (X-IL less than or similar to 0.3), the IL behaves as a conventional but strongly associated electrolyte.