Effect of Patch Size and Attraction Energy on Polymer Chain Adsorption in Slits Created by Opposing Patch-Patterned Surfaces

Abstract

The adsorption behavior of a polymer chain within a slit composed of two patch-patterned surfaces is investigated using Langevin dynamics simulations. Each surface exhibits periodic attractive square patches (period d, size L, attraction energy ε_ps), with a 0.5d misalignment between the two surfaces. The adsorption degree increases with L, while the mean number of occupied patches <n_pa> and the surface-parallel component of the mean square radius of gyration <R²_g,xy> exhibit a complex dependence on L. We identify distinct adsorption regimes: a single-surface and single-patch adsorbed state for L > L_s, an upper-lower and multi-patch adsorbed state for L > L_m, and a complete adsorbed state for L > L_c. At weak ε_ps, the polymer chain adopts single-surface and single-patch adsorption for middle L and upper-lower and multi-patch adsorption for large L. Conversely, a strong ε_ps promotes upper-lower and multi-patch adsorption for small L, and single-surface and single-patch adsorption as L increases. The adsorption degree increases monotonically to saturate with ε_ps, while <n_p> initially increases and subsequently decays toward stability. Notably, <R²_g,xy> first decreases, then increases, and finally decreases to stabilize as ε_ps increases. These results highlight the role of patch geometry and interaction strength in governing polymer adsorption behavior.