Molecular Scale Hydrophobicity in Varying Degree of Planar Hydrophobic Nanoconfinement

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We have studied the molecular scale hydrophobicity of an apolar solute, argon, confined between hydrophobic planar surfaces with different confinement widths. Specifically, we find that the hydrophobicity exhibits a non-monotonic behavior with confinement width. While hydrophobicity is usually large compared to bulk value, we find a narrow range of confinement width where the hydrophobicity displays similar values as in bulk water. Furthermore, we develop a simple model taking into account the entropic changes in nanoconfined geometry, which enables us to calculate potential of mean force between solutes as the conditions change from bulk to different degrees of planar nanoconfinement. Our results are important in understanding nanoconfinement induced stability of apolar polymers, solubility of gases, and may help design better systems for Enhanced Oil Recovery.