Regensburg 2004 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 8: Physics of Polymers II
CPP 8.2: Talk
Monday, March 8, 2004, 16:00–16:15, H 37
Hypersonic relaxation in glass-formers: Thermodynamic theory and experimental studies using Brillouin spectroscopy — •Jörg Baller1,2, Jan Kristian Krüger1,2, Thomas Britz1,2, Wulff Possart1,3, Wolfgang Manglkammer1,2, and Roland Sanctuary1,4 — 1Laboratoire Européen de Recherche Universitaire Saarland-Lorraine (LERUSL) — 2Universität des Saarlandes, Fakultät für Physik und Elektrotechnik 7.2, Geb. 38, D-66041 Saarbrücken, Germany — 3Universität des Saarlandes, Fakultät für Chemie, Pharmazie und Werkstoffwissenschaften 8.15, Geb. 22, D-66041 Saarbrücken, Germany — 4Universitaire du Luxembourg, 162a av. de la Faïencerie, L-1511 Luxembourg, Luxembourg
The presented work gives a theoretical framework for the relaxation behaviour of the elastic moduli of glass-formers near the glass transition temperature. Using linear irreversible thermodynamics, an expression for the temporal evolution of the elastic moduli (measured at hypersonic frequencies) after a step-like change of temperature is calculated. These theoretical results are compared to measurements of the hypersonic elastic modulus by Brillouin Light Scattering (BLS). Three different materials - an oligomer, an epoxy resin and a classical polymer - have been examined by measuring the relaxation behaviour of the hypersound velocity after a temperature pertubation. A discussion of the importance and the influence of thermodynamic equilibrium during accomplishment of an relaxation experiment is given by comparison to the theoretical results.