Discrete-to-continuum simulation approach to polymer chain systems: Subdiffusion, segregation, and chain folding

A discrete-to-continuum approach is introduced to study the static and dynamic properties of polymer chain systems with a bead-spring chain model in two dimensions. A finitely extensible nonlinear elastic potential is used for the bond between the consecutive bends with the Lennard-Jones (LJ) potential with smaller (R-c=2(1/6)sigma=0.95) and larger (R-c=2.5 sigma=2.1) values of the upper cutoff for the nonbonding interaction among the neighboring beads. We find that chains segregate at temperature T=1.0 with R-c=2.1 and remain desegregated with R-c=0.95. At low temperature (T=0.2), chains become folded, in a ribbonlike conformation, unlike random and self-avoiding walk conformations at T=1.0. The power-law dependence of the rms displacements of the center of mass (R-c.m.) of the chains and their center node (R-cn) with time are nonuniversal, with the range of exponents nu(1) similar or equal to 0.45-0.25 and nu(2) similar or equal to 0.30-0.10, respectively. Both radius of gyration (R-g) and average bond length ([I]) decrease on increasing the range of interaction (R-c), consistent with the extended state in good solvent to collapsed state in poor solvent description of the polymer chains. Analysis of the radial distribution function supports these observations.