Adsorption and diffusion of a polymer chain within a thin slit composed of two patch-patterned surfaces

Abstract

The adsorption and diffusion behaviors of a polymer chain within a narrow slit composed of two patch-patterned surfaces is studied using Langevin dynamics simulations. The surfaces consist of a neutral area interspersed with periodic attractive patches of size L and period d. The mismatch of the upper and lower surfaces is denoted by Δx and Δy along x- and y-directions. For both the perfectly matched system (Δx = Δy = 0) and the mismatched system (Δx = 0.5d, Δy = 0) with moderate sized patches, the polymer chain mainly adopts an upper-lower adsorption state, i.e., it is adsorbed on both surfaces simultaneously. However, for the mismatched system with Δx = Δy = 0.5d, a single-surface adsorption state where the polymer is adsorbed on only one surface is primarily observed. On the other hand, the polymer chain does not undergo diffusion in the matched case, but exhibits normal diffusion on a long time scale in mismatched cases. The translational diffusion coefficient increases when the patch mismatch changes from Δx = 0.5d, Δy = 0 to Δx = Δy = 0.5d, which is attributed to an increased frequency of changes in the adsorption state. The polymer chain diffuses via a patch-exchange mode, that is, it exchanges patches between an upper-lower adsorption state and a single-surface adsorption state. The effect of patch period and slit height is also studied. These findings underscore the pivotal role of patch mismatch in modulating polymer adsorption and diffusion behaviors.