By a simple DTA system, the glass transition temperatures of the quaternary ammonium type ionic liquid, {N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium iodide, [DEME][I] + H2O} mixtures after quick pre-cooling were measured as a function of water concentration (x mol% H2O). Results were compared with the previous results of ([DEME][BF4]+ H2O) mixtures in which double glass transitions were observed in the water concentration region of (16.5 to 30.0) mol% H2O. Remarkably, we observed the double glass transition phenomenon in {[DEME][I]+ H2O} mixtures too, but the two-T(g)s regions lie towards the water-rich side of (77.5 to 85.0) mol% H2O. These clearly reflect the difference in the anionic effect between BF4- and I- on the water structure. The end of the glass-formation region of {[DEME][I] + H2O} mixtures is around x = 95.0 mol% H2O, and this is comparable to that of {[DEME][BF4]+ H2O} mixtures (x = 96.0 mol% H2O). (C) 2010 Elsevier Ltd. All rights reserved.