The results described above indicate that the layered distribution is either a stable or metastable structure. To confirm either of these, samples that had settled for a more extended period of time were analyzed. showing that the layered interfacial structure disappeared in ~20 h. This disappearance was explained as a structural relaxation from a layered distribution to a random-coiled configuration of the PDMS. The disappearance of the layered ∆f distribution in our study can be explained in the same way. The relaxation time of 9750 mPa•s PDMS on mica was 74-142 h in our study, while those of 97 mPa•s PDMS on Si 7 and 480 mPa•s PDMS on silicon oxide 9 was ~4 h and ~20 h, respectively. That is, these results indicate that the relaxation time required for disappearing the layered distribution increases with the viscosity. Note that, in this experiment, the shear caused by the spin coating might be an additional cause of the persistence of this structure for a long time, but this is unlikely because no significant difference in the ∆ƒ and ∆γ distribution was observed with or without spin coating in the experiment using PDMS with a viscosity of 970 mPa•s (Supporting Information: Figure ).