Abstract
Liquid-liquid transition of water is an important concept in condensed-matter physics. Recently, it was claimed to have been confirmed in aqueous solutions based on annealing-induced upshift of glass-liquid transition temperature, . Here we report a universal water-content, , dependence of for aqueous solutions. Solutions with vitrify/devitrify at a constant temperature, , referring to freeze-concentrated phase with left behind ice crystallization. Those solutions with totally vitrify at under conventional cooling/heating process though, of the samples annealed at temperatures to effectively evoke ice recrystallization is stabilized at . Experiments on aqueous glycerol and 1,2,4-butanetriol solutions in literature were repeated, and the same samples subject to other annealing treatments equally reproduce the result. The upshift of by annealing is attributable to freeze-concentrated phase of solutions instead of ‘liquid II phase of water’. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution.
Highlights
Devitrification process, begins to appear on the heating curve at a temperature T gI
We report systematic measurement of the water-content dependence of glass transition temperature for various aqueous solutions in an as wide as possible range of concentration, which reveals a universal behavior that can set criteria to divide the solutions into three distinct zones
We noticed that for the medium-concentration aqueous solutions, glass-liquid transition can be complicated by ice recrystallization in the heating process depending on the thermal history, and the liquid phase II corresponds to the freeze-concentrated phase, i.e., the portion of the solution of an elevated but definite concentration resulting from water freezing, of the annealed solutions
Summary
Devitrification process, begins to appear on the heating curve at a temperature T gI. In those solutions with Xaqu > Xacqru, precipitation of primary ice occurs at first in the cooling process (a pronounced endothermal peak appears prior to the glass transition on DSC curve, see Supplementary Fig. 1a), glass-liquid transition temperatures stabilized at a constant value, Tg′, were measured, which arises from the devitrification of the freeze-concentrated phase.
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