Metastable Vapor in a Janus Nanoconfinement

BS Jabes and J Driskill and D Vanzo and D Bratko and A Luzar, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 13144-13150 (2017).

DOI: 10.1021/acs.jpcc.7b02147

We study the competition between liquid and vapor states of water confined between diametrically different surfaces, one hydrophilic and the other strongly hydrophobic (Janus interface). Using atomistic simulations and a generalization of the capillarity approximation, we demonstrate that vapor bubbles can persist in the confinement in long- lived metastable states. In contrast to the well-known metastability of confined liquid with respect to capillary evaporation, a strongly metastable vapor phase has so far not been anticipated, as infiltration does not involve the formation of new liquid-vapor interfaces. In the case of a Janus interface, however, we show that the interfacial free energy passes through a pronounced maximum during infiltration. This counterintuitive phenomenon provides a new mechanism for water-mediated attraction (capillary force) between polar and nonpolar surfaces in biophysical systems and in dispersions of heterogeneous nanoparticles.

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