Density Functional Theory of Square-well Chain Mixtures Near Solid Surface

Abstract

A density functional theory is developed for square-well chain mixtures near a hard wall or a square-well wall. The Helmholtz free energy functional is divided into two parts, an ideal-gas contribution and an excess contribution. The later is constructed based on weighting density approximation and coarse graining approximation. For simplicity, a Heaviside function is used as the weighting function. To calculate the density profiles of beads, a direct iterative algorithm combined with a relaxation factor is used. A single chain simulation in an effective field is needed in each iterative step. The theoretical results are in good agreement with Monte Carlo simulation.