Discrepancies in the characterization of the glass transition in thin films of hyperbranched polyesters

The dynamic glass transition and the dilatometric glass transition temperature are simultaneously characterized in thin films of hyperbranched aromatic polyesters by broadband dielectric spectroscopy and capacitive scanning dilatometry. A diverging thickness dependence is detected: while the tempera...

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Bibliographic Details
Published in:Journal of polymer science. Part B, Polymer physics Polymer physics, 2006-10, Vol.44 (20), p.3006-3010
Main Authors: Serghei, A., Mikhailova, Y., Eichhorn, K.-J., Voit, B., Kremer, F.
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
glass transition
molecular dynamics
Organic polymers
Physicochemistry of polymers
Properties and characterization
Thermal and thermodynamic properties
thin films
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Summary:The dynamic glass transition and the dilatometric glass transition temperature are simultaneously characterized in thin films of hyperbranched aromatic polyesters by broadband dielectric spectroscopy and capacitive scanning dilatometry. A diverging thickness dependence is detected: while the temperature position of the alpha relaxation peak Tα decreases by ∼30 K, the dilatometric Tg increases by ∼10 K with decreasing film thickness. This emphasizes the subtle character of the glass transition phenomenon—as manifested in the molecular dynamics and in the (structural) thermal expansion—and proves that, in contrast to the bulk, different experimental techniques do not necessarily deliver similar results in confinement. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3006–3010, 2006
ISSN:0887-6266
1099-0488
DOI:10.1002/polb.20929