A distinctive property of liquid water is its ability to strongly screen Coulomb interactions between charged and polar species. This strong dielectric nature of liquid water underlies most aspects of life, from Earth’s biogeochemical cycles to solvation, transport, and phase separation in biological structures. A key fundamental question associated with the dielectric nature of liquid water, motivated by the importance of interfacial and confined water in most natural and engineered systems, is its modulation by proximity to nearby interfaces. Here, we address this question by using molecular dynamics (MD) simulations of water to examine the frequency-dependent dielectric properties of liquid water in interlayer nanopores of the prototypical smectite swelling clay mineral. Notably, we observe a drastic (ten-fold) and anisotropic decrease in the static permitivitty of the system as the pore width decreases from 5 to 0.3 nm. Our results reveal that water confined in clay interlayer nanopores (and possibly in other charged nanopores) is a distinct solvent with a much weaker collective nature than bulk liquid water.

Dielectric spectra of water in charged clay interlayer nanopores

ACS Spring Meeting 2021

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