We studied liquid water confined within nanopores which present a high level of hydrophobicity thanks to a new method of synthesis. We found that the liquid state persists down to temperatures much lower than in the bulk and in hydrophilic materials of comparable sizes, allowing us to define a thermodynamic limit for the melting/crystallization of water.

Significance: Studying water crystallization at low temperature and the lower limit of ice formation is crucial both for a fundamental understanding of water and for practical reasons such as cryopreservation. By taking advantage of the polarized neutron scattering technique and by considering a nanosegregated water–glycerol solution, we are able to characterize the key parameters of ice formation at temperatures near and below the calorimetric glass transition of the solution and provide a general rule for estimating the lower temperature limit of water crystallization in a broad range of aqueous solutions. We also show that nanosegregated water in the glassy solution at low temperature is not in a high-density form but in a low-density one.