Cryosuction and freezing hydrogels

Source abstract

Recent experiments have shown a rich variety of behaviour when soft, brittle, hydrogels are frozen, since water cannot freeze within the pore space of these materials as a result of the Gibbs–Thompson effect. Hence, no ice forms within the hydrogel matrix, and pure ice grows by cryosuction, drawing water from the surrounding gel towards the phase boundary. The growth of this ice leads to deformation of the poroelastic gel, and drives interstitial flows in the nanoscale pores within the remaining dried hydrogel. In this paper, we model the formation of ice when hydrogels are cooled at a fixed surface, and investigate both the rate at which the ice grows and the elastic response of the gel that remains, explaining the steady states seen in experiments and the processes by which damage can be effected on the hydrogel. Understanding these freezing behaviours is vitally important if we are to comprehend the mechanisms behind damage to porous media such as asphalt road surfaces or human organs when they are frozen, and how to mitigate such effects.