  Using dielectric spectroscopy and differential scanning calorimetry, we have
performed a detailed investigation of the influence of water uptake on the
translational and reorientational glassy dynamics in the typical ionic liquid
1-Butyl-3-methyl-imidazolium chloride. From a careful analysis of the measured
dielectric permittivity and conductivity spectra, we find a significant
acceleration of cation reorientation and a marked increase of the ionic
conductivity for higher water contents. The latter effect mainly arises due to
a strong impact of water content on the glass temperature, which for the
well-dried material is found to be larger than any values reported in
literature for this system. The fragility, characterizing the non-Arrhenius
glassy dynamics of the ionic subsystem, also changes with varying water
content. Decoupling of the ionic motion from the structural dynamics has to be
considered to explain the results.
