title: Correlated heterogeneous dynamics in glass-forming polymers.
abstract: We report x-ray photon correlation spectroscopy experiments on the dynamics of the glass-former polypropylene glycol covering a temperature range from room temperature to the glass transition at T(g)=205 K using silica tracer particles. Three temperature regimes are identified: At high temperatures, Brownian motion of the tracer particles is observed. Near T(g), the dynamics is hyperdiffusive and ballistic. Around 1.12T(g), we observe an intermediate regime. Here the stretching exponent of the Kohlrausch-Williams-Watts function becomes q dependent. By analyzing higher-order correlations in the scattering data, we find that dynamical heterogeneities dramatically increase in this intermediate-temperature regime. This leads to two effects: increasing heterogeneous dynamics and correlated motion at temperatures close to and below 1.12T(g).
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Conrad
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.|The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Lehmkühler
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Fischer
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Westermeier
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.|The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany.
authors.forename: M A
authors.initials: MA
authors.lastname: Schroer
authors.affiliation: European Synchrotron Radiation Facility, Avenue des Martyrs 71, 38000 Grenoble, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Chushkin
authors.affiliation: University of Siegen, Walter-Flex Straße 3, 57072 Siegen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Gutt
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Sprung
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.|The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Grübel