In contrast, the previous static-mode AFM study performed on 480 mPa•s PDMS/Si interface showed that the oscillatory force profile was observed soon after the deposition of the PDMS (≤ 30 min). This difference can be explained by the entanglement of the PDMS molecules. In general, the effects of entanglement on the bulk physical properties become significant for the polymers with the critical entanglement molecular weight Mc. The viscosity of the bulk liquid increases drastically above Mc. The Mc of PDMS is approximately 21,000-33,000, which corresponds to the viscosities of about 590-1200 mPa•s. Therefore, the PDMS used in this experiment has a much higher molecular weight than Mc, whereas that used in the previous report with static-mode AFM To discuss the mobility of the liquid molecules in more detail, we obtained ∆γ-z curves simultaneously with the ∆f-z curves. Figures The residual ∆γ -∆γhyd can be regarded as originating from the dissipative interaction between the tip and the interfacial structure. the molecules on the interface. However, the oscillation period of ∆γ was inconsistent with that of ∆ƒ, reflecting the density distribution, and this oscillation was not observed in the layered distribution region on the 29 h-settling sample (Figure ). To clarify the origin of the oscillation, further AFM study on polymer melt/solid interfaces would be required.