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 <i>L</i> and period <i>d</i>, with a staggered configuration of (0.5<i>d</i>, 0.5<i>d</i>) offsets along the <i>x</i> and <i>y</i> axes. When <i>d</i> is fixed, the polymer chain exhibits normal diffusion over long time scales, with the translational diffusion coefficient <i>D</i>_<i>xy</i> gradually decreasing to zero as <i>L</i> increases. Notably, our findings reveal four distinct diffusion modes: free-diffusion mode for <i>L</i> ≤ <i>L</i>₁, where the polymer chain is mainly in a desorption state; adsorption-desorption mode for <i>L</i>₁ < <i>L</i> ≤ <i>L</i>₂, involving transitions from a single-patch adsorption state to a desorption state; exchange-patch mode for <i>L</i>₂ < <i>L</i> ≤ <i>L</i>₃, 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 <i>L</i> > <i>L</i>₃, where the polymer chain is primarily in a pinned state. Furthermore, as the patch attraction strength ε_ps increases, <i>D</i>_<i>xy</i> decreases due to an increase in the adsorption time of the polymer chain. Simultaneously, critical patch size thresholds <i>L</i>₁, <i>L</i>₂, and <i>L</i>₃, exhibit a decreasing trend. These observations highlight the significant influence of the confining slit and patch properties on the diffusion behavior of polymer chains.