| Abstract |
The thermal and dielectric properties of ionic liquid 1-butyl-3-methylimidazolium bromide (BmimBr) were measured in the glassy, supercooled liquid and equilibrium liquid states, covering the temperature range from -120 to 100 degrees C. From thermally stimulated depolarization current (TSDC) data we determined the glass transition temperature, that was in very good agreement with the calorimetric one (T-g = -48 degrees C). The kinetic parameters associated to the main relaxation, i.e. activation energy and the pre-exponential factor, were also estimated. From dielectric relaxation spectroscopy (DRS), two sub-T-g relaxations were clearly detected. One of them presents a good correlation with that also detected using TSDC, and exhibiting characteristics compatible with those of a genuine Johari-Goldstein secondary process. Additionally, the temperature dependence of d.c. conductivity obeys the Vogel-Fulcher-Tammann-Hesse (VFTH) equation. The degree of decoupling between charge transport and the structural alpha-relaxation was also estimated for BmimBr. |
