Structural relaxation in poly(ethylene oxide)-salt solutions

We present the results of molecular dynamics simulations of PEO_xNaI polymer electrolytes, performed to study the influence of NaI on the dynamics of PEO. By calculating the mean square displacement of the CH₂ groups we observe that the Rouse-like motion, typical for short polymer chains, is slowed down under the influence of NaI. This slowing down is also observed in the self part of the intermediate scattering function F^s(k,t), as an increase in the relaxation time. By using the Gaussian approximation it is shown that the stretched exponential relaxation in the small k-limit of F^s(k,t) is a result of the Rouse-like motion of the polymers. We find that our results are in good agreement with neutron spin-echo experiments.