Behavior of water at different interfaces and under nanoconfinement

L. M. ALARCÓN; J. A. RODRÍGUEZ FRIS; S. R. ACCORDINO; J. M. MONTES DE OCA; G. A. APPIGNANESI

Iguazu

Congreso; 13th International Conference on Properties and Phase Equilibria for Products and Process Design; 2013

A full comprehension of the behavior of water under nanoconfinement, usually quite different from that at bulk conditions, is still far from being complete. In this work we present some studies of water at different interfaces (ranging from simple model hydrophobic interfaces to protein surfaces) and confinement conditions. Our studies reveal the fact that the first water hydration layers tend to be better structured than the bulk and highly oriented, even resembling the structure of hexagonal ice. In such way the water molecules of the first layer sacrifice the lowest possible water-water hydrogen bond (HB) coordination. This tendency to maximize the number of HBs also reflects itself in cavity filling, since small subnanometric cavities remain empty given the cost to resign HB coordination, while larger cavities show an alternation of filled and dry states with important HB patterns. These constraints imposed by the confinement and the hydrophobic interactions usually prevent the water molecules from displaying bulk-like behavior. Thus, the relevance of this kind of knowledge to biology and to the design of new materials will be pointed out by highlighting the context-dependence and non-additive nature of different con-covalent interactions in an aqueous environment, an issue that is usually greatly overlooked.