Abstract
We report a detailed study of the main structural and dynamical features of water confined in model Lennard–Jones nanopores with tunable hydrophobicity and finite length ( Å). The generic model of cylindrical confinement used is able to reproduce the wetting features of a large class of technologically and biologically relevant systems spanning from crystalline nanoporous materials, to mesoporous silica and ion channels. The aim of this work is to discuss the influence of parameters such as wall hydrophobicity, temperature, and pore size on the structural and dynamical features of confined water. Our simulation campaign confirmed the existence of a core domain in which water displays bulk-like structural features even in extreme ( Å) confinement, while dynamical properties were shown to depend non-trivially on the size and hydrophobicity of the pores.This article is part of the theme issue ‘Progress in mesoscale methods for fluid dynamics simulation’.
Highlights
The present work reports a study of the structural and dynamical properties of water in extreme confinement by means of molecular dynamics (MD) simulations
To further understand the type of the hydrogen bonds (HBs) for the contact and inner layer, we reported in figure 6b the fraction of water molecules belonging to the contact layer engaging in nHB HBs with a molecule belonging to the same layer and with the inner layer
We have studied by means of molecular dynamics simulations the structure and dynamics of water confined inside model cylindrical nanopores with three levels of hydrophobicity, two different radii and at temperatures ranging from those of biological interest to colder ones
Summary
The present work reports a study of the structural and dynamical properties of water in extreme confinement by means of molecular dynamics (MD) simulations. When the wall surface presents chemical groups that can strongly hydrogen bond water, surface water was found to become nearly immobile, while the core water still showed bulk-like dynamics [26] Such local mobility effects were found, in the case of silica pores, to have experimentally observable consequences on the macroscopic flow [30,31]. The present results indicate that, even for very high confinements (pore radius R = 7.0 Å), a core of water is preserved that displays some degree of bulk-like local structural features This surprising behaviour seems connected to the lack of surface charges on the pore walls and hydrogen bonds between water and pore atoms. Translational dynamical properties have been measured to be more sensitive to the confinement, with different dependencies on the pore size and hydrophobicity observed for diffusion along the pore axis and over the pore section
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