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Article Dans Une Revue Proceedings of the National Academy of Sciences of the United States of America Année : 2012

Activated drying in hydrophobic nanopores and the line tension of water

Résumé

We study the slow dynamics of water evaporation out of hydro-phobic cavities by using model porous silica materials grafted with octylsilanes. The cylindrical pores are monodisperse, with a radius in the range of 1–2 nm. Liquid water penetrates in the nanopores at high pressure and empties the pores when the pressure is lowered. The drying pressure exhibits a logarithmic growth as a function of the driving rate over more than three decades, showing the ther-mally activated nucleation of vapor bubbles. We find that the slow dynamics and the critical volume of the vapor nucleus are quantita-tively described by the classical theory of capillarity without adjust-able parameter. However, classical capillarity utterly overestimates the critical bubble energy. We discuss the possible influence of surface heterogeneities, long-range interactions, and high-curvature effects, and we show that a classical theory can describe vapor nucleation provided that a negative line tension is taken into account. The drying pressure then provides a determination of this line tension with much higher precision than currently available methods. We find consistent values of the order of −30 pN in a variety of hydrophobic materials. drying transition | hydrophobicity | kinetics | nanobubbles |
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Dates et versions

hal-01087836 , version 1 (26-11-2014)

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Ludivine Guillemot, Thierry Biben, Anne Galarneau, Gérard Vigier, Élisabeth Charlaix. Activated drying in hydrophobic nanopores and the line tension of water. Proceedings of the National Academy of Sciences of the United States of America, 2012, 109 (48), pp.19557. ⟨10.1073/pnas.1207658109⟩. ⟨hal-01087836⟩
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