Molecular Scale Hydrophobicity in Varying Degree of Planar Hydrophobic Nanoconfinement

TL;DR

This study investigates how the hydrophobicity of argon molecules changes under different degrees of planar nanoconfinement, revealing non-monotonic behavior and developing a model to predict interactions in confined environments.

Contribution

It introduces a simple entropic model to predict hydrophobicity and solute interactions under nanoconfinement, advancing understanding of molecular behavior in confined spaces.

Findings

Hydrophobicity varies non-monotonically with confinement width.

A narrow confinement range shows bulk-like hydrophobicity.

The model predicts potential of mean force changes with confinement.

Abstract

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.