Abundant low-frequency motions in the poly(methyl methacrylate) (PMMA) phase of polymer blends of poly(propylene oxide) epoxy and thermoplastic PMMA with submicron morphologies are revealed by solid-state NMR measurements. The presence of this mobility is in Line with the depression of glass temperatures in thin polymer films. The modified polymer dynamics induced by microscopic morphology is potentially important for research on frequency-dependent polymer conductivity, dynamics in polymeric glasses, physical aging, and models for polymer fracture dynamics.