Dynamics in thin polymer films by dielectric spectroscopy

After a brief review on the recent developments of the dielectric studies in thin polymer films, our recent results on dynamics in thin films of poly(methyl methacrylate) (PMMA) and polyisoprene (PIP) are shown. For PMMA, the tacticity effect on dynamics in thin films has been investigated and the disappearance of this effect was found below a critical thickness. For PIP, the motion of entire polymer chains, namely, the normal mode, has been investigated. The dielectric-loss spectrum of the normal mode is much more sensitive to the decrease in film thickness than that due to the alpha-process. The broadening of dielectric-loss spectra of the normal mode is observed for film thicknesses below about 150 nm, while the position of the loss peak does not change in the thickness range down to about 50 nm. Anomalous increase in dielectric loss between the alpha-process and the normal mode was observed, which is consistent with the recent report on the existence of an additional relaxation process.