Freeze-thaw behaviour of aqueous glucose solutions--the crystallisation of cubic ice.
We report on the polymorphic transitions of ice in aqueous solutions of glucose during freezing and thawing over a temperature range of 298-153 K. Emphasis is placed on the sub-glass temperature range where the systems consist of cubic ice (ice-1c) crystals embedded in a freeze concentrated, vitrified glucose solution. The systems were studied by a combination of thermal, cryomicroscopic and X-ray diffraction techniques. At the glass transition (230 K) the solution phase contained 80 mol% of unfrozen water which, on further cooling, was shown to crystallise as cubic ice (ice-1c), nucleated in the vitrified matrix. The thermal stability of the ice-1c formed was studied by annealing and isothermal changes in the diffraction patterns with time. The polymorphic transition 1c --> 1h could be fitted to first order kinetics. Contrary to currently held belief, this study has provided evidence that ice-1c can be formed directly in the bulk water phase of a vitrified solution.
Thanatuksorn
Pariya
P
School of Bionics, Tokyo University of Technology, 1404-1 Katakura, Hachioji, Tokyo, 192-0982, Japan.
Kajiwara
Kazuhito
K
Murase
Norio
N
Franks
Felix
F