The microscopic polymer dynamics in nanocomposite polymer electrolytes has been investigated using quasielastic neutron scattering experiments. Four samples based on the fully amorphous copolymer trihydroxy poly(ethylene oxide-co-propylene oxide) (3PEG) were investigated: 3PEG, 3PEG 1.5 mol/kg LiClO4, 3PEG 1.5 mol/kg LiClO4 10 wt % TiO2, and 3PEG 1.5 mol/kg LiClO4 20 wt % TiO2. In addition to a slow relaxation giving rise to elastic scattering, at least two dynamical processes were observed: a fast, local chain motion and a slower diffusive segmental motion. No changes of the quasielastic peak widths could be observed between the filled or unfilled composites; however, the elastic scattering of the sample was found to increase upon addition of the filler to the polymer electrolyte. The results indicate the presence of a roughly 5-nm-thick immobilized polymer layer (similar to5 vol %) around filler particles, while the dynamics of the bulk polymer (similar to95 vol %) is not influenced by the filler. The results imply that the ionic conductivity increase observed in the nanocomposite polymer electrolyte cannot be attributed to enhanced polymer dynamics. (C) 2003 American Institute of Physics.