Melt Structure and Dynamics of Unentangled Polyethylene Rings: Rouse Theory, Atomistic Molecular Dynamics Simulation, and Comparison with the Linear Analogues

Abstract

Atomistic configurations of model unentangled ring polyethylene (PE) melts ranging in chain length from C24 up to C400 have been subjected to detailed molecular dynamics (MD) simulations in the isothermal−isobaric statistical ensemble at temperature T = 450 K and P = 1 atm. Strictly monodisperse samples were employed in all cases. We present and discuss in detail simulation results for a variety of structural, thermodynamic, conformational and dynamic properties of these systems, and their variation with chain length. Among others, these include the mean chain radius of gyration, the pair correlation function, the intrinsic molecular shape, the local dynamics, the segmental mean square displacement (msd), the chain center-of-mass self-diffusion coefficient DG, the chain terminal relaxation time τd, the characteristic spectrum of the Rouse relaxation times τp, and the dynamic structure factor S(q,t). In all cases, the results are compared against the corresponding data from simulations with linear PE melts...