Berlin 2015 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 47: P12: Glasses and Glass Transition
CPP 47.4: Poster
Mittwoch, 18. März 2015, 10:00–13:00, Poster A
Glass transition coopeativity from broad band heat capacity spectroscopy — •Yeong Zen Chua1, Gunnar Schulz1, Evgeni Shoifet1, Heiko Huth1, Reiner Zorn2, Jürn W.P. Schmelzer1, and Christoph Schick1 — 1Institute of Physics, University of Rostock, Wismarsche Str. 43-45, 18051 Rostock, Germany — 2Juelich Centre for Neutron Science, 52425, Juelich, Germany
Molecular dynamics is often studied by broad band dielectric spectroscopy (BDS) because of the wide dynamic range available and the large number of processes resulting in electrical dipole fluctuation and with that in a dielectrically detectable relaxation process. Calorimetry on the other hand is an effective analytical tool to characterize phase and glass transitions by its signatures in heat capacity. In the linear response scheme, heat capacity is considered as entropy compliance. Consequently, only processes significantly contributing to entropy fluctuations appear in calorimetric curves. The glass relaxation is prominent example for such a process. Here we present complex heat capacity at the dynamic glass transition (segmental relaxation) of polystyrene (PS) and poly(methyl methacrylate) (PMMA) in a dynamic range of 11 orders of magnitude, which is comparable to BDS. As one of the results, we determine the temperature dependence of the characteristic length of the corresponding fluctuations. The characteristic length decreases from about 4 nm to about 0.7 nm in the temperature range from 370 K to 500 K. This proves an estimate for possible confinement effects on the segmental relaxation, which is different from vitrification as discussed by Cangialosi et al.