Pathways to dewetting in hydrophobic confinement

Richard C. Remsing, Erte Xi, Srivathsan Vembanur, Sumit Sharma, Pablo G. Debenedetti, Shekhar Garde, Amish J. Patel, Ken A. Dill

Research output: Contribution to journalArticle

64 Scopus citations

Abstract

Liquid water can become metastable with respect to its vapor in hydrophobic confinement. The resulting dewetting transitions are often impeded by large kinetic barriers. According to macroscopic theory, such barriers arise from the free energy required to nucleate a critical vapor tube that spans the region between two hydrophobic surfaces-tubes with smaller radii collapse, whereas larger ones grow to dry the entire confined region. Using extensive molecular simulations of water between two nanoscopic hydrophobic surfaces, in conjunction with advanced sampling techniques, here we show that for intersurface separations that thermodynamically favor dewetting, the barrier to dewetting does not correspond to the formation of a (classical) critical vapor tube. Instead, it corresponds to an abrupt transition froman isolated cavity adjacent to one of the confining surfaces to a gap-spanning vapor tube that is already larger than the critical vapor tube anticipated by macroscopic theory. Correspondingly, the barrier to dewetting is also smaller than the classical expectation. We show that the peculiar nature of water density fluctuations adjacent to extended hydrophobic surfaces- namely, the enhanced likelihood of observing low-density fluctuations relative to Gaussian statistics-facilitates this nonclassical behavior. By stabilizing isolated cavities relative to vapor tubes, enhanced water density fluctuations thus stabilize novel pathways, which circumvent the classical barriers and offer diminished resistance to dewetting. Our results thus suggest a key role for fluctuations in speeding up the kinetics of numerous phenomena ranging from Cassie-Wenzel transitions on superhydrophobic surfaces, to hydrophobically driven biomolecular folding and assembly.

Original languageEnglish (US)
Pages (from-to)8181-8186
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number27
DOIs
StatePublished - Jul 7 2015

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Assembly
  • Capillary evaporation
  • Fluctuations
  • Kinetic barriers

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