posted on 2024-02-01, 17:36authored byYuriy G. Bushuev, Yaroslav Grosu, Mirosław Chorążewski
The properties of
nanoconfined fluids are important for a broad
range of natural and engineering systems. In particular, wetting/dewetting
of hydrophobic nanoporous materials is crucial due to their broad
applicability for molecular separation and liquid purification; energy
storage, conversion, recuperation, and dissipation; for catalysis,
chromatography, and so on. In this work, a rapid, orchestrated, and
spontaneous dipole reorientation was observed in hydrophobic nanotubes
of various pore sizes d (7.9–16.5 Å)
via simulations. This phenomenon leads to the fragmentation of water
clusters in the narrow nanopores (d = 7.9, 10 Å)
and strongly affects dewetting through cluster repulsion. The cavitation
in these pores has an electrostatic origin. The dependence of hydrogen-bonded
network properties on the tube aperture is obtained and is used to
explain wetting (intrusion)–dewetting (extrusion) hysteresis.
Computer simulations and experimental data demonstrate that d equals ca. 12.5 Å is a threshold between a nonhysteretic
(spring) behavior, where intrusion–extrusion is reversible,
and a hysteretic one (shock absorber), where hysteresis is prominent.
This work suggests that water clustering and the electrostatic nature
of cavitation are important factors that can be effectively exploited
for controlling the wetting/dewetting of nanoporous materials.