A discrete-to-continuum (DC) simulation approach is introduced to study the statics and dynamics of polymer chains in two dimensions with quenched barriers, a dirty surface. In our DC hybrid approach, the large-scale relaxation of polymer chains on a discrete disordered lattice is followed by off-lattice simulation using a bead-spring chain model with a finitely extensible nonlinear elastic (FENE) potential for covalent bonds and Lennard-Jones (LJ) potential for nonbonded interactions. Segregation/folding of chains, which occurs at low temperatures (T = 0.2, 1.0) with LJ interaction, becomes more difficult as the concentration of barriers increases, due to a screening effect of the barriers. In contrast to the chains' contraction at high temperature (i.e., T = 5) and their collapse in athermal systems, chains are elongated on increasing the barrier concentration-a barrier-induced stretching. Variations of the root-mean-square (rms) displacements of the center of mass (R-cm) of the chains and their center node (R-cn) with time (t) show power-law behaviors (R-cm similar to t(nu 1), R-cn similar to t(nu 2)) with nonuniversal exponents in the range nu(1) similar or equal to 0.40-0.05 and nu(2) similar or equal to 0.30-0.05, respectively, depending on temperature and barrier concentration. The radius of gyration (R-g) and the average bond length ([l]) expand on increasing the barrier concentration at low temperature and contract at high temperature, which is consistent with the variation of the width of the radial distribution function. (C) 1998 American Institute of Physics. [References: 29]
展开▼
