Structure and dynamics of dilute two-dimensional ring polymer solutions

Abstract

Structure and Dynamics of dilute two-dimensional (2D) ring polymer solutions are investigated by using discontinuous molecular dynamics simulations. A ring polymer and solvent molecules are modeled as a tangent-hard disc chain and hard discs, respectively. Some of solvent molecules are confined inside the 2D ring polymer unlike in 2D linear polymer solutions or three-dimensional polymer solutions. The structure and the dynamics of the 2D ring polymers change significantly with the number (N in) of such solvent molecules inside the 2D ring polymers. The mean-squared radius of gyration (R 2) increases with N in and scales as R ∼ N v with the scaling exponent v that depends on N in. When N in is large enough, v ≈ 1, which is consistent with experiments. Meanwhile, for a small Ni n ≈ 0.66 and the 2D ring polymers show unexpected structure. The diffusion coefficient (D) and the rotational relaxation time (x rot) are also sensitive to Ni n: D decreases and τ increases sharply with Nin. D of 2D ring polymers shows a strong size-dependency, i.e., D ∼ ln(L), where L is the simulation cell dimension. But the rotational diffusion and its relaxation time (τ rot) are not-size dependent. More interestingly, the scaling behavior of τ rot also changes with N in; for a large Ni n τ rot ∼ N 2.46 but for a small N in τ rot ∼ N 1.43.