Interfacial structure of a solute-solvent mixture in contact with a semipermeable membrane

Abstract

A nonlinear theory for the calculation of interfacial structural properties of a solute-solvent mixture in contact with a semipermeable

membrane has been developed.The membrane is permeable to the solvent but impermeable to the solute. The theory is based on a

density functional approach where the solute density and the isotropic part of the solvent density are calculated by a weighted density

approximation and the anisotropic part of the solvent density is calculated by a perturbative approach. Explicit numerical results are

obtained for the interfacial structure of a solute-solvent mixture in contact with a semipermeable membrane on varying the width ,

surface charge density and permeability of the membrane and the solute-solvent size ratio. The density profiles of both the solute and

the solvent are found to be highly inhomogeneous and oscillatory near the membrane surface. The density near the membrane is found

to increase with decreasing permeability and also with increasing su rface charge density of the membrane. The solvent polarization

profiles reveal pronounced orientational order of the solvent molecules near a charged membrane. The predictions of the present theory

are compared with the results of Monte Carlo simulations and a good agreement is found for the inhomogeneous structure in the

interfacial region.