Restricted primitive model for electrolyte solutions in contact with solid surface modified by grafted chains: A density functional approach

We have studied the microscopic structure and the thermodynamic and electric properties of the restricted primitive model for electrolyte solutions in contact with a chemically modified uncharged and charged solid surface. The modification of the surface is performed by the tethering of chain particles via a specific single segment at the stage preceeding the adsorption of the restricted primitive model. Some fraction of segments belonging to a chain particle can be charged such that the system models adsorption on an electrode covered by an electrolyte brush. We apply the density functional method which combines previously developed approach for inhomogeneous chain fluids, and the weighted density mean spherical approximation energy route for the description of inhomogeneous ionic fluids. The theory is formulated in the semigrand canonical ensemble. Our principal findings are concerned with the density profiles of the species, the adsorption isotherms of ions in the presence of grafted chain particles, the charge density profile and the potential of zero charge (all as the functions of the grafted density), and other parameters related to the solid surface and its modification. (c) 2008 American Institute of Physics.