The dynamic in polyethyleneoxide-alkali iodide complexes investigated by neutron spin-echo spectroscopy and molecular dynamics simulations

摘要

We determii~ed the self ~t ~ ~ ucattenug llmction in liquid polyethyleneoxide (PEO) and PEO—alkai means of neutron spin-echo spectroscopy and molezular dynau~cs (MD) ~ sinuilatiofis. We present the first accurate quantitative results on the seginemmi dyinuics in the time range up to 1 ns and the wave-vector range from a few nm1 to approxinia~r 20w’. W~ investigate the influence of polymer chain length, salt concentration, and cki. iyp.~ We, finA~ ~ the neutron data and MD data for pure PEO agree veiy well. A relatively small concentration of dissolved salt (1 metal ion per 15 monomers) leads to a slowing dwn of the segmental motions by an order of magnitude. Here, the MD simulations agree qualitatively, increasing the chain length from 23 to 182 monomers has no significant effect except at the highest salt concentration. Similarly, changing the cation from Li to Na hardly makes anydiffsrence. The Rouse model does not adequately describe our data.