Title

Conformation and dynamics of interacting polymer chains in a porous medium

Document Type

Article

Publication Date

7-15-1997

Department

Physics and Astronomy

Abstract

Monte Carlo simulations are performed to study the conformational and dynamical properties of interacting polymer chains with counterion solvent background in porous media generated by a random distribution of quenched barriers of concentration p(b), We study the dependence of the radius of gyration (R-g) of chains and variation of their rms displacement (R-rms) with time, on the polymer concentration (p) chain length (L-c), temperature (T) and porosity (p(s) = 1 - p(b)) as these parameters cooperate and compete. In homogensous/annealed systems (p(b) = 0), the power-law exponent gamma for the radius of gyration of the chains shows a crossover from SAW-conformation with gamma similar to 0.61 at low polymer concentrations (dilute regime p = 0.001-0.01) to an ideal chain conformation with gamma similar to 0.52 for chain concentrations p = 0.1-0.3 in three dimensions at high temperatures. In porous media, we observe a crossover from an SAW-like conformation with gamma similar to 0.64 at high porosities (p(s) greater than or equal to 0.8) to a collapse conformation with gamma similar to 0.35 at low porosities (p(s) less than or equal to 0.5 at temperature T = 1.0. The rms displacement of the chains is generally diffusive, R-rms = At-0.5, at low p and high T while it is subdiffusive R-rms = At-k, with k < 0.5 at high p and low T, For example, k similar or equal to 0.2 at p = 0.3 and T = 1.0 in three dimension in annealed systems. In quenched porous media, the motion is generally subdiffusive (at p(b) greater than or equal to 0.2 in three dimension, but becomes ultra-subdiffusive with R-rms = At-k, where k < 0.1 at low temperatures, The prefactor A shows a power-law dependence on the chain length, A similar to L-c(-u), except at high polymer concentrations and low temperature, with the exponent mu similar to 0.45-0.57 in annealed systems and similar to 0.53-0.64 in porous media at p = 0.3.

Publication Title

PHYSICA A

Volume

241

Issue

3-4

First Page

500

Last Page

517