DYNAMICS OF LATTICE MODELS OF POLYMER-CHAINS NEAR THE 0 POINT

Dynamic Monte Carlo simulations were performed for isolated polymer chains on both simple cubic and face-centered cubic lattices with a rigorous excluded-volume constraint and a nearest-neighbor interaction, ϵ (i.e., a square well potential) between the nonbonded beads of the chain. The chains were observed to exhibit Rouse-like dynamics in the good solvent (or high-temperature) regime and for repulsive interactions. Relaxation times of the normal coordinates, τ, were fit to the scaling relations τ (N, k) ~ (N – 1)αk τ (N, k) ~ k-γN where N is the number of beads in the chain and k is the mode number, αk was observed to be dependent on k for the values of ϵ studied and γN was found to be dependent on N – 1 as the θ point was approached. Above the θ point the scaling behavior for the two lattices was the same for a given value of μϵ, where μ is the effective coordination number (the coordination number of the lattice minus 1). For the short chains studied the θ point was observed to be at approximately μϵ = -1.8kBT. Near and below the θ point, however, the dynamics of both models are significantly different from the Rouse prediction, probably due to the increasing lifetime of nearest-neighbor pair contacts. This observation is consistent with the concept of gel modes introduced by Brochard and De Gennes. © 1990, American Chemical Society. All rights reserved.