Glass transition cooperativity from broad band heat capacity spectroscopy

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...

Full description

Saved in:
Bibliographic Details
Published in:Colloid and polymer science 2014-08, Vol.292 (8), p.1893-1904
Main Authors: Chua, Yeong Zen, Schulz, Gunnar, Shoifet, Evgeni, Huth, Heiko, Zorn, Reiner, Scmelzer, Jürn W. P., Schick, Christoph
Format: Article
Language:English
Subjects:
Applied sciences
Characterization and Evaluation of Materials
Chemistry
Chemistry and Materials Science
Complex Fluids and Microfluidics
Exact sciences and technology
Food Science
Nanotechnology and Microengineering
Organic polymers
Original Contribution
Physical Chemistry
Physicochemistry of polymers
Polymer Sciences
Properties and characterization
Soft and Granular Matter
Thermal and thermodynamic properties
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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.
ISSN:0303-402X
1435-1536
DOI:10.1007/s00396-014-3280-2