Diffusivities and Viscosities of Poly(ethylene oxide) Oligomers

The Publisher Version is available at: http://pubs.acs.org/doi/pdf/10.1021/je100430qDiffusivities and viscosities of poly(ethylene oxide) (PEO) oligomer melts of 1 to 12 repeat units have been obtained from equilibrium molecular dynamics simulations using the TraPPE-UA force field. The simulations generate diffusion coefficients with high accuracy for all molecular weights studied, but statistical uncertainties for the viscosity calculations significantly increase for longer chains. There is in good agreement of calculated viscosities and densities with available experimental data. The simulations can be used to fill in gaps in the data and for extrapolations with respect to chain length, temperature and pressure. We have explored the convergence characteristics of the Green-Kubo formulae for different chain lengths and propose minimal production times required for convergence of the transport properties. The chain length dependence of transport properties suggests that neither Rouse nor reptation models are applicable in the short-chain regime investigated.This publication is based on work supported by Award No. KUS-CI-018-02 made by King Abdullah University of Science and Technology (KAUST). This paper is dedicated to Sir John Rowlinson or his many contributions to experiment, theory and history of thermodynamics and for his mentorship of one of us (AZP) at a critical and formative time