Chapter 5
The Thermal Glass Transition Beyond the Time Trap
Downloaded by UNIV OF SOUTHERN CALIFORNIA on July 20, 2013 | http://pubs.acs.org Publication Date: January 28, 1999 | doi: 10.1021/bk-1998-0710.ch005
K.-P. Bohn, and J. K. Krüger FB 10.2 Experimentalphysik, Universität des Saarlandes, 66041 Saabrücken, Germany
High performance Brillouin spectroscopy was used to investigate the temperature dependent behavior of the longitudinal acoustic mode, the refractive index, and the hypersonic longitudinal mode Grüneisen parameter around the quasi-static glass transition temperature T of Polyvinylacetate. In the glass transition zone the longitudinal mode Grüneisen Parameter γ shows an apparent anomaly with a step-like anomaly. Whereas the temperature position of this anomaly clearly depends on the thermal history of the sample, the amplitude Δ = γL(Τ>Τ )-γ (T