Phase diagram of confined water

Despite the intensive studies of interfacial and confined water, many aspects of its behavior remain not well studied or even unclear. There are only a few studies of the phase diagram of confined water and of water adsorbed on the surface. Most of these studies are the simulations with very simple smooth surfaces. Clearly, experimental studies and simulations with more realistic surfaces are necessary. Repulsion between hydrophilic surfaces in liquid water gained much less attention than attraction between hydrophobic surfaces. However, this effect may be responsible, for example, for the destruction of some solids in environment with varying humidity. The liquid-liquid transitions of water, confined in various pores, should be studied because of their importance not only in understanding the properties of interfacial water but also aiming to locate these transitions in bulk water. 

The effects of the intramicellar confinement of polar and amphiphilic species in nanoscopic domains dispersed in an apolar solvent on their physicochemical properties (electronic structure, density, dielectric constant, phase diagram, reactivity, etc.) have received considerable attention [51,52]. hi particular, the properties of water confined in reversed micelles have been widely investigated, since it simulates water hydrating enzymes or encapsulated in biological environments [13,23,53-59]. 

The model coexistence curves for our choice of s — 3.0 are shown in Fig. 4.18. The shaded areas indicate regions of phase coexistence of the confined system. The remarkable ehange of the phase diagram relative to that of the bulk system is caused by the strong confinement together with the strong selectivity of the pore for water. As expected, the critical temperature of the pore fluid is shifted downward. The critical composition has moved toward the water-rich side because of the selective character of the substrates. 

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