In many biological and chemical systems, such as pockets of proteins and catalyst pores, water is found in geometries of nanoscopic dimensions. Such �confined water� has attracted attention because of its importance in biological processes such as protein folding, as well as its supercritical-like phase behavior at ambient conditions. This suggests that the phase behavior of confined water can be mapped onto the supercritical region of bulk water. We have developed a method to measure local structural and thermodynamic properties in order to study the phase behavior of confined water under varying pressure and confining surface properties (such as hydrophobicity and patterning).Previous molecular dynamics simulations have shown that water confined between hydrophobic surfaces exhibits large changes in density in response to relatively small changes in pressure. We will present a sampling method to calculate local dielectric constant, isothermal compressibility, and structural order parameters to understand how the confining walls induce metastable properties. We also seek to relate these measurables to properties characteristic of supercritical water.The supercritical nature of confined water might make it an alternative, �greener� medium for reactions that are currently run in supercritical water, such as hazardous waste oxidation and novel materials synthesis, because it avoids the expensive and energy-consuming conditions of supercritical water. Using local measurements of water phase behavior, we seek to understand how the confinement parameters and metastable signatures of confined water can be harnessed to promote these reactions.

Local dynamics of water in confined geometry

248th National Meeting (2014)

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