title: Segmental relaxations have macroscopic consequences in glassy polymer films.
abstract: We have investigated the consequences of physical aging in thin spin-coated glassy polystyrene films through detailed dewetting studies. A simultaneous and equally fast exponential decay of dewetting velocity, width, and height of the rim with aging time was observed, which is related to a reduction of residual stresses within such films. The temperature dependence of these decay times followed an Arrhenius behavior, yielding an activation energy of 70±6 kJ/mol, on the same order of magnitude as values for the β-relaxation of polystyrene and for relaxations of surface topographical features. Our results suggest that rearrangements at the level of chain segments are sufficient to partially relax frozen-in out-of-equilibrium local chain conformations, i.e., the cause of residual stresses, and they might also be responsible for macroscopic relaxations at polymer surfaces.
authors.affiliation: Physikalisches Institut, Albert-Ludwigs-Universität, 79104 Freiburg, Germany. mch.mater@gmail.com
authors.forename: Mithun
authors.initials: M
authors.lastname: Chowdhury
authors.forename: Paul
authors.initials: P
authors.lastname: Freyberg
authors.forename: Falko
authors.initials: F
authors.lastname: Ziebert
authors.forename: Arnold C-M
authors.initials: AC
authors.lastname: Yang
authors.forename: Ullrich
authors.initials: U
authors.lastname: Steiner
authors.forename: Günter
authors.initials: G
authors.lastname: Reiter