Conformation of interacting polymer chains: Effects of temperature, bias, polymer concentration, and porosity

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Physics and Astronomy


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 (p(s)) on the magnitude of the radius of gyration (R-g) of the chains and its scaling with the chain length (L-c) are studied. In an annealed system, we observe a crossover in power-law variation of the radius of gyration with the chain length, R-g similar to L-c(gamma), from an extended conformation with gamma similar or equal to 0.7 at low bias (B=0.2), low p, and high T to a collapsed conformation with gamma similar to 0.20-0.31 at high bias (B greater than or equal to 0.5) and low T. In a quenched porous medium, we observe a somewhat lower value of the power-law exponent, gamma similar to 0.60-0.70, from its annealed value at high T and low bias. At low temperatures, in contrast, the magnitude of gamma similar to 0.39-0.47 is enhanced with respect to its annealed value. Various nonlinear responses of R-g to bias are observed in different ranges B, L-c, p(s), and T. In particular, we find that the response is nonmonotonic at low temperatures (T similar or equal to 0.1) in the annealed system and at high temperatures (T similar or equal to 100.0) in a porous medium with a relatively high barrier concentration (p(b) greater than or equal to 0.3).

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