Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 29: Polymerphysics I
CPP 29.5: Vortrag
Donnerstag, 28. Februar 2008, 10:30–10:45, C 130
Generalized mode-Grüneisen-parameters as a universal measure for the chemically induced glass transition in reactive systems — •Ulrich Müller1, Martine Philipp1, Jan Kristian Krüger1, Roland Sanctuary1, Wulff Possart2, Bartosz Zielinski1, Jörg Baller1, Ravindrakumar Bactavatchalou1, Patrick Alnot3, and Christelle Vergnat1 — 1Université du Luxembourg, LPM, Campus Limpertsberg, L-1511 Luxembourg — 2Universität des Saarlandes, ASPG, 66041 Saarbrücken — 3Université Henri Poincaré - Nancy I, Nancy, France
A fundamental understanding of the glass transition is still lacking and so the controversy about the nature of the glass transition, being it a kinetic or intrinsic transition, is going on. The investigation of an isothermal cure of reactive systems by means of generalized mode-Grüneisen-parameters (gMGP) offers an alternative access to this problem. In contrast to the MGP known from solid state physics being sensitive to changes of elastic anharmonicity (3rd order elasticity), gMGP probe in addition 2nd order elasticity modified by structural changes during the curing process. Using epoxies and polyurethanes as model systems and combining Brillouin spectroscopy with high resolution refractometry the temporal evolution of the related gMGP indicate indeed the onset of chemical freezing. The comparison with caloric data suggests that there is a rough coincidence of the gGMP anomaly and the vanishing excess heat capacity with respect to the heat capacity of the glassy state.