Glass Transition Behavior of the Quaternary Ammonium-Type Ionic Liquid: N,N-Diethyl-N-methyl-N-(2-methoxyethyl)ammonium Bromide-H2O Mixtures

By a simple differential thermal analysis (DTA) system, the concentration dependence of the glass transition temperatures (s) for the quaternary ammonium-type ionic liquid, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bromide [DEME][Br] and H2O mixtures, after quick precooling was measured as a function of water concentration (mol% H2O). We compared the results with the previous results of [DEME][I]-H2O and [DEME][BF4]-H2O mixtures in which a double-glass transition behavior was observed. Remarkably, the [DEME][Br]-H2O mixtures basically show one- behavior and the decreases monotonically with increasing H2O content up to around =91.5. But it suddenly jumps to higher value at a specific =～92. At this very limited point, two s (1,2) which we might consider as a transition state from the structure belonging to the 1 group to another one due to the 2 group were observed. These results clearly reflect the difference in the anionic effects among Br−, I−, and BF4？. The end of the glass-formation region of [DEME][Br]-H2O mixtures is around =98.9 and moves to more water-rich region as compared to those of [DEME][BF4]-H2O (=96.0) and [DEME][I]-H2O (=95.0) mixtures.