Viscosity of supercooled aqueous glycerol solutions, validity of the Stokes-Einstein relationship, and implications for cryopreservation

J. TREJO GONZALEZ; M. PAULA LONGINOTTI; H. R. CORTI

CRYOBIOLOGY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Bedfordshire; Año: 2012 vol. 65 p. 159 - 162

0011-2240

The viscosity of supercooled glycerol aqueous solutions, with glycerol mass fractions between 0.70 and 0.90, have been determined to confirm that the Avramov-Milchev equation describes very well the temperature dependence of the viscosity of the binary mixtures including the supercooled regime. On contrary, it is shown that the free volume model of viscosity, with the parameters proposed in a recent work (He, Fowler and Toner, J. Appl. Phys. 100 (2006) 074702), overestimates the viscosity of the glycerol-rich mixtures at low temperatures by several orders of magnitude. Moreover, the free volumen model for the water diffusion leads to predictions of the Stokes-Einstein product, which are incompatible with the experimental findings. We conclude that the use of these free volume models, with parameters obtained by fitting experimental data far from the supercooled and glassy regions, lead to incorrect predictions of the deterioration rates of biomolecules, overestimating their life time in these cryopreservation media.