The segmental and local chain dynamics as well as the transport of Na+ and Li+ cations in a series of model poly(ethylene oxide)-based polyurethane ionomers is investigated using dielectric relaxation spectroscopy. A physical model of electrode polarization is employed to separately determine mobile ion concentration and ion mobility in these single-ion conductors. A model including unpaired ions, separated ion pairs, and contact ion pairs is used to reconcile the very small fraction of free ions obtained using the electrode polarization model with those of previous studies of ion association in polyether-based single-ion conducting and salt-containing systems.