Thermodynamic properties of aqueous organic mixtures near the critical demixing: Cases of 2,6-dimethylpyridine and of 2-isobutoxyethanol

Prewetting transition influenced by layeringlike transitions at a binary liquid/solid interface

“…The bulk liquid mixture undergoes a liquid-liquid demixing with a lower critical point at T C ϭ13.1°C, and several solid-liquid demixings down to 0°C. 15,16,19 In the liquid two-phase system in contact with silica, a wetting transition takes place at T W Х46°C, the complete wetting being between T C and T W and the water-rich phase the bulk wetting phase. 3͑a͒ A previous study shows 15͑a͒ that the system undergoes layering, i.e., surface solidlike-liquid demixing.…”

Thermodynamic properties of aqueous solution of 2-isobutoxyethanol atT= (293.15, 298.15, and 303.15) K, below and above LCST

“…However, such negative contributions may be attributed to negative divergence of C E p,m due to the fluctuation in composition on approaching the LCST. The fluctuation of concentration occurs over a considerably wider region than the real phase separation reported by Perron et al (6) and Stephenson, (8) though we cannot give a theoretical approach to the behaviour of thermodynamics of LCST. The mixture of 2-isobutoxyethanol and water is considered to consist of two states, as a mixture of an alcohol and water.…”

“…Perron and coworkers reported that this system has LCST at x = 0.052 and T = 298.8 K and phase separation in the region 0.025 < x < 0.15 at T = 303.15 K. (6) Zimmer and his coworkers also reported LCST at T = 299.60 K. (7) Stephenson, however, reported phase separation in the region 0.03 < x < 0.10 at T = 298.15 K and the region 0.018 < x < 0.175 at T = 303.15 K. (8) The small linear part found in the H E m against x curve corresponds to the phase separation region. However, it seems to shift to higher x and be wide as compared to the reports by Perron et al (6) and Stephenson. (8) The flat part of H E m at T = 298.15 K is due to the approach to phase separation.…”

“…However, experimental results for 2-isobutoxyethanol solutions are scarce except for those of density and refractive index (5) and demixing to phase separation. (6)(7)(8) The 2-isobutoxyethanol also self-associates by hydrogen bonding between the alcoholic OH group and the partially ether O atom and by hydrophobic interaction between isobutoxyethyl groups as 2-ethoxyethanol and 2-isopropoxyethanol. In the aqueous 2-isobutoxyethanol solution, the existence of two types of associated cluster or mixing states is expected.…”

“…The other is a hydrophobic-interacted (aggregated by alkoxyethyl group) cluster surrounded by water molecules, which are hydrogen bonded with alcoholic OH, similar to a micromicelle. The existence of lower critical consolute temperature (LCST) is reported in the aqueous 2-isobutoxyethanol solution near T = 298 K. (6)(7)(8) Excess thermodynamic properties of the aqueous 2-isobutoxyethanol solution may enhance the more complicated behaviour by appearance of macroscopic phase separation as a result of two mixing states. We have reported on the thermodynamic properties of (methoxyethanol + cyclohexane) at the temperatures above and below upper critical consolute temperature (UCST) (10) and systematic studies of the excess thermodynamic properties of (alkoxyethanol + n-octane).…”