TY  - JOUR
AU  - Chua, Yeong Zen
AU  - Schulz, Gunnar
AU  - Shoifet, Evgeni
AU  - Huth, Heiko
AU  - Zorn, Reiner
AU  - Scmelzer, Jürn W. P.
AU  - Schick, Christoph
TI  - Glass transition cooperativity from broad band heat capacity spectroscopy
JO  - Colloid & polymer science
VL  - 292
IS  - 8
SN  - 1435-1536
CY  - Berlin
PB  - Springer
M1  - FZJ-2014-04619
SP  - 1893 - 1904
PY  - 2014
AB  - 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 fluctuations 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 a 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 determined the characteristic length scale of the corresponding fluctuations. The dynamic glass transition measured by calorimetry is finally compared to the cooling rate dependence of fictive temperature and BDS data. For PS, dielectric and calorimetric data are similar but for PMMA with its very strong secondary relaxation process some peculiarities are observed.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000339888900015
DO  - DOI:10.1007/s00396-014-3280-2
UR  - https://juser.fz-juelich.de/record/155453
ER  -