Local dielectric spectroscopy, which entails measuring the change in resonance frequency of the conducting tip of an atomic force microscope to determine the complex permittivity of a sample with high spatial (lateral) resolution, was employed to characterize the dynamics of thin films of poly(vinyl methyl ketone) (PVMK) having different substrate and top surface layers. A free surface yields the usual speeding up of the segmental dynamics, corresponding to a glass transition suppression of 6.5° for 18 nm film thickness. This result is unaffected by the presence of a glassy, compatible polymer, poly-4-vinyl phenol (PVPh), between the metal substrate and the PVMK. However, covering the top surface with a thin layer of the PVPh suppresses the dynamics. The speeding up of PVMK segmental motions observed for a free surface is absent due to interfacial interactions of the PVMK with the glass layer, an effect not seen when the top layer is an incompatible polymer.