Using an off-lattice Monte Carlo bead-spring model of a chain in a random environment, we study chain conformations and dynamic scaling of diffusivity and relaxation times with chain length N and density of the host matrix ${\mathrm{C}}_{\mathrm{obs}}$. Our simulational results show that with growing ${\mathrm{C}}_{\mathrm{obs}}$ the mean size (gyration radius) of the polymer, ${\mathrm{R}}_{\mathrm{g}}^2$, initially slightly decreases and then rapidly increases as the macromolecule exceeds the size of the average entropic wells and stretches through bottlenecks into neighboring wells. The chain dynamics changes from a Rouse-like one into a reptational one as the permeability of the matrix decreases. Although at variance with some previous treatments [M. Muthukumar, J. Chem. Phys. 90, 4594 (1989)], these findings agree well with a recent analytic approach (S. V. Panyukov, Zh. Éksp. Teor. Fiz. 103, 1287 (1993) [Sov. Phys. JETP 76, 631 (1993)]) to chain conformations in random media. We also suggest a simple scaling analysis, based on a ``blob'' representation of the polymer chain, whereby the blob size is governed by the size of the cavities in the host matrix and yields a faithful description of our computer experiments.

• Received 15 August 1996

DOI:https://doi.org/10.1103/PhysRevE.55.1704