How Molecular Orientation Affects the Static Permittivity Profile of the Polar and Nonpolar Liquid-Liquid Interface

20 February 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The dielectric permittivity across the liquid-liquid interface presents an intrinsic response with respect to the instantaneous interface reference. We hypothesize that dielectric responses across the nonpolar and polar liquid-liquid interfaces have different behaviors and with different underlying mechanisms. Molecular dynamics simulations were used to compare and contrast the dielectric response of a nonpolar (1,2-dichloroethane/water) and polar (1-octanol/water) liquid-liquid interface system. We found that enhanced dielectric permittivity at the nonpolar interface is attributed to the increased water dipole orientation and polarization density. In the case of the polar interface, strong association of the immiscible solvents inhibit the molecular dipole orientation, counteracting the effect from the enhanced surface water polarization density and resulting in a standard dielectric response. Detailed knowledge of the hydrogen bond networks and molecular dipole orientation with respect to the specific instantaneous interfacial and bulk regions reveals the effect of molecular proximity and the interaction with the opposing interfacial molecules upon the mechanism of the dielectric permittivity response across the liquid-liquid interface phase boundary.


dielectric permittivity
polar and nonpolar
liquid-liquid interface
molecular dynamics simulation


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