The transport properties of rod-like particles. II. Narrow slit pore

We investigate the behavior of rigid macromolecules in narrow slit pores. Molecular dynamics studies are reported for hard, infinitely thin rods between semi-infinite pore walls. The rod rotational motion exhibits an "entangled" regime at high concentrations similar to that observed in the bulk fluid. However the transition to the entangled regime takes place at a higher concentration in the pore. At concentrations well below the transition concentration, the pore translational diffusion coefficient exceeds the corresponding bulk diffusivity. At concentrations near or above the transition concentration, the pore diffusivity drops below the bulk diffusivity, and is only weakly dependent upon concentration. The translational motion is "Knudsen-like" in this regime, with the diffusion coefficient primarily determined by rod-wall collisions.