title: Glass transition dynamics of stacked thin polymer films.
abstract: The glass transition dynamics of stacked thin films of polystyrene and poly(2-chlorostyrene) were investigated using differential scanning calorimetry and dielectric relaxation spectroscopy. The glass transition temperature T(g) of as-stacked thin polystyrene films has a strong depression from that of the bulk samples. However, after annealing at high temperatures above T(g), the stacked thin films exhibit glass transition at a temperature almost equal to the T(g) of the bulk system. The α-process dynamics of stacked thin films of poly(2-chlorostyrene) show a time evolution from single-thin-film-like dynamics to bulk-like dynamics during the isothermal annealing process. The relaxation rate of the α process becomes smaller with increase in the annealing time. The time scale for the evolution of the α dynamics during the annealing process is very long compared with that for the reptation dynamics. At the same time, the temperature dependence of the relaxation time for the α process changes from Arrhenius-like to Vogel-Fulcher-Tammann dependence with increase of the annealing time. The fragility index increases and the distribution of the α-relaxation times becomes smaller with increase in the annealing time for isothermal annealing. The observed change in the α process is discussed with respect to the interfacial interaction between the thin layers of stacked thin polymer films.
authors.affiliation: Department of Physics, Ritsumeikan University, Noji-Higashi 1-1-1, Kusatsu 525-8577, Japan. fukao.koji@gmail.com
authors.forename: Koji
authors.initials: K
authors.lastname: Fukao
authors.forename: Takehide
authors.initials: T
authors.lastname: Terasawa
authors.forename: Yuto
authors.initials: Y
authors.lastname: Oda
authors.forename: Kenji
authors.initials: K
authors.lastname: Nakamura
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tahara