Filling of Water in Hydrophilic Nanopores

EZEQUIEL DE LA LLAVE; ESTEFANA GONZALEZ SOLVEYRA; DAMIAN A. SCHERLIS PEREL; MOLINERO, VALERIA

Holderness, NH, EE.UU.

Conferencia; Gordon Research Conference on Chemistry & Physics of Liquids; 2009

Gordon Research Conference

Molecular dynamics simulations of water in cylindrical hydrophilic pores with diameters of 1.5 and 3 nm were performed to explore the phase behavior and the nucleation dynamics of the confined fluid as a function of the percentage of volume filled f. The interactions of water with the pore wall were considered to be identical to the interactions between water molecules. At low water contents, all the water is adsorbed to the surface of the pore. A second phase consisting of a liquid plug appears at the onset filling for capillary condensation, fonset=27% and 34% for the narrow and wide pores, respectively. After condensation, two phases, a liquid plug and a surface-adsorbed phase, coexist in equilibrium. Under conditions of phase coexistence, the water surface density was found to be independent of the water content and the diameter of the pore, with a value of􏰋3 nm−2􏰈, in good agreement with experimental results for silica pores, suggesting that the interactions of water with silica and with itself are comparable. The surface-adsorbed phase at coexistence is a sparse monolayer with a structure dominated by small water clusters. We characterize the density and structure of the liquid and surface phases, the nucleation mechanism of the water plug, and the effect of surface hydrophilicity on the two-phase equilibrium and hysteresis.