DIFFUSION OF A POLYMER-CHAIN THROUGH A THIN MEMBRANE

We study the configurational and dynamic properties of a long polymer chain during the process of penetration of the chain through the thin and porous membrane. The mobility of a polymer in this state depends s trongly on the topological restrictions imposed by the membrane. The l argest mobility have configurations in which the polymer chain crosses the membrane only once and diffuses through a single pore from one si de of the membrane to the other. This configuration may have small sta tistical weight compared to other configurations with low mobility in which the polymer chain crosses the membrane many times. The relative weight of these configurations depends also on the chemical potential of the membrane. We find the configurations which give the main contri bution to the transport and calculate the overall permeability of the membrane for Zimm and Rouse mechanisms of polymer dynamics.