How does confinement in nano-scale pores change the thermodynamic properties and the nature of phase transitions of water?

TL;DR

This paper investigates how nanoscale confinement alters water's thermodynamic properties and phase transition behavior, revealing that freezing point depression is a macroscopic effect and that confined water undergoes a collective phase transition similar to bulk water.

Contribution

It demonstrates that water's freezing point depression in nanopores is a macroscopic phenomenon and that the phase transition remains collective, describable by macroscopic thermodynamics.

Findings

Freezing temperature can be significantly lowered in nanopores.

Freezing transition remains a collective phenomenon similar to bulk water.

Thermodynamics of confined water can be related to bulk water through Laplace pressure.

Abstract

We analyze thermodynamics of water samples confined in nanopores and prove that although the freezing temperature can be dramatically lower, the suppression of the ice nucleation leading to the freezing temperature depression is a truly macroscopic effect rather than a consequence of microscopic interactions. The freezing transition itself is a truly collective phenomenon described by a macroscopic order parameter (the nearly homogeneous density of the liquid within the pore away from the pores wall) exactly in the same way as in the bulk liquid. The thermodynamics properties of the confined and the bulk liquid can be described by macroscopic thermodynamics and be readily related to each other simply by proper inclusion of the additional Laplace pressure exerted by the solid-liquid boundary.