Document Type

Article

Publication Date

4-1-1997

Department

Physics and Astronomy

School

Mathematics and Natural Sciences

Abstract

The conformations of interacting polymer chains driven by a biased field in heterogeneous media are studied using Monte Carlo simulations in three dimensions. In addition to excluded volume, a nearest-neighbor interaction is considered with polymer-polymer repulsion and polymer-solvent attraction. Two types of heterogeneous media are considered: (i) a homogeneous-annealed system consisting of mobile polymer chains and solvents and (ii) quenched porous media, generated by adding a random distribution of quenched barriers. Effects of polymer concentration (p), bias (B), temperature (T), and porosity (ps) on the magnitude of the radius of gyration (Rg) of the chains and its scaling with the chain length (Lc) are studied. In an annealed system, we observe a crossover in power-law variation of the radius of gyration with the chain length, Rg∼Lyc, from an extended conformation with γ≃0.7 at low bias (B=0.2), low p, and high T to a collapsed conformation with γ∼0.20-0.31 at high bias (B⩾0.5) and low T. In a quenched porous medium, we observe a somewhat lower value of the power-law exponent, γ∼0.60-0.70, from its annealed value at high T and low bias. At low temperatures, in contrast, the magnitude of γ∼0.39-0.47 is enhanced with respect to its annealed value. Various nonlinear responses of Rg to bias are observed in different ranges of B, Lc, ps and T. In particular, we find that the response is nonmonotonic at low temperatures (T≃0.1) in the annealed system and at high temperatures (T≃100.0) in a porous medium with a relatively high barrier concentration (pb⩾0.3)

Comments

©Physical Review E

Publisher Version

Publication Title

Physical Review E

Volume

55

Issue

4

First Page

4433

Last Page

4441

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