Figure 1. Glass transition of aqueous solutions complicated by annealing-induced ice recrystallization.
(a) Glass transition temperature, 
, against the mass fraction of water, 
, for glycerol solutions (empty circle) obtained under conventional cooling/heating process. In those
solutions with a 
, ice precipitation occurs first in cooling process. The freeze-concentrated phases vitrify at a constant 
, and the corresponding 
can be directly read from the monotonous part of the 
vs. 
curve at the point where 
. Here 
= 170 K, 
, 
. For comparison, 
data for the liquid I (blue solid circle) and liquid II (olive solid circle) phases of water in glycerol solution with 
reported in ref. 18 are presented. (b) Solution mass-normalized heat flow change at glass transition, 
, as a function of 
for glycerol solutions. The blue and red hollow triangles in (a,b) denote the data points for freeze-concentrated phases of glycerol solutions with 
and 
subjected to temperature protocol 2 and protocol 4 (see below), respectively. (c) DSC thermograms for three distinct temperature protocols demonstrated with the glycerol solution of 
. Protocol 1 (black line): Conventional cooling/heating process; protocol 2 (blue line): The cooling process is terminated at 167 K and maintained there for 230 min., followed by heating to room temperature; protocol 3 (orange line): The heating process is interrupted at 167 K and maintained there for 230 min. After that the sample was again cooled down to 113 K and then heated to room temperature. (d) Protocol 4: The heating process is interrupted at 194 K. After maintained there for 1 min. to complete ice recrystallization, the sample was again cooled down to 113 K and then heated to room temperature. Arrows pointing at the curves indicate where 
is extracted. (e,f) 
versus 
for aqueous solutions of 1,2,4-butanetriol and AlCl3, respectively. For the former,
= 175 K, 
, 
; for the latter, 
= 154 K, 
, 
. Again, the blue (protocol 2) and red (protocol 4) triangles corresponding to measurements with annealing treatment, and data from ref. 19 (solid circles), are presented.