The ideal polymer chain near planar hard wall beyond the Dirichlet boundary conditions

Abstract

We present a new ab initio approach to describe the statistical behavior of long ideal polymer chains near a plane hard wall. Forbidding the solid half-space to the polymer explicitly (by the use of Mayer functions) without any other requirement, we derive and solve an exact integral equation for the partition function G (D)(r,r', N) of the ideal chain consisting of N bonds with the ends fixed at the points r and r'. The expression for G(r,r', s) is found to be the sum of the commonly accepted Dirichlet result G (D)(r,r', N) = G (0)(r,r', N) - G (0)(r,r'', N) , where r'' is the mirror image of r', and a correction. Even though the correction is small for long chains, it provides a non-zero value of the monomer density at the very wall for finite chains, which is consistent with the pressure balance through the depletion layer (so-called wall or contact theorem). A significant correction to the density profile (of magnitude 1/[Formula: see text]is obtained away from the wall within one coil radius. Implications of the presented approach for other polymer-colloid problems are discussed.