Investigation of Polymer Chain Diffusion Behavior in Thin Slits Formed by Patch-Patterned Surfaces: Influence of Patch Properties

The diffusion dynamics of polymer chains within a narrow slit formed by two patch-patterned surfaces is investigated utilizing Langevin dynamics simulations. These surfaces feature periodically arranged attractive patches of size L and period d, with a staggered configuration of (0.5d, 0.5d) offsets along the x and y axes. When d is fixed, the polymer chain exhibits normal diffusion over long time scales, with the translational diffusion coefficient D_xy gradually decreasing to zero as L increases. Notably, our findings reveal four distinct diffusion modes: free-diffusion mode for L ≤ L₁, where the polymer chain is mainly in a desorption state; adsorption–desorption mode for L₁ < L ≤ L₂, involving transitions from a single-patch adsorption state to a desorption state; exchange-patch mode for L₂ < L ≤ L₃, where the polymer chain switches between a single-patch adsorption state and an upper-lower double-patch adsorption state by exchanging patches; and nondiffusion mode for L > L₃, where the polymer chain is primarily in a pinned state. Furthermore, as the patch attraction strength ε_ps increases, D_xy decreases due to an increase in the adsorption time of the polymer chain. Simultaneously, critical patch size thresholds L₁, L₂, and L₃, exhibit a decreasing trend. These observations highlight the significant influence of the confining slit and patch properties on the diffusion behavior of polymer chains.