Equilibrium dynamics in the nondiffusive regime of an entangled polymer blend

The dynamics of compositional fluctuations in a miscible, entangled homopol ymer blend of poly(ethylene oxide) and poly(methyl methacrylate) were studi ed on length scales smaller than the polymer radii of gyration, and for tim es comparable to the polymers' disentanglement time. The measured relaxatio n rates are consistent with predictions of the reptation model, as expresse d via the dynamic random-phase approximation. Moreover, the observed mode a mplitudes allow for an estimate of the entanglement length in the blend.