Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 43: Nanoparticles and Composite Materials I
CPP 43.6: Vortrag
Donnerstag, 17. März 2011, 15:30–15:45, ZEU 222
Free volume of interphases in model nanocomposites studied by positron annihilation lifetime spectroscopy — Stephan Harms1, •Klaus Rätzke1, Franz Faupel1, Gerald J. Schneider2, Lutz Willner2, and Dieter Richter2 — 1Materialwissenschaft-Materialverbunde , Universität Kiel, 24143 Kiel — 2Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich
Free volume studies were performed in nanocomposites by positron annihilation lifetime spectroscopy (PALS) to explore the influence of the interphase nanoscale character of the hydrophobically functionalized filler particles and the nanoscale particle size on positron parameters [1]. A weakly repulsive system, not forming an interphase, was obtained by mixing of low molecular weight poly(ethylene-alt-propylene) (PEP) and hydrophobically modified silica with varying concentration. DSC experiments showed a constant glass transition temperature Tg and a decrease in heat capacity at Tg with increasing filler concentration. In contrast, PALS measurements showed decreasing Tg and a strong drop of the thermal expansion coefficient above Tg. These seemingly conflicting results are due to nanoscale character of filler particles with sizes in the range of the positronium diffusion length. This requires taking into account out-diffusion of positronium from the particles. In particular, the changes on PALS parameters with increasing filler content cannot be attributed to the formation of an interphase with properties different from the polymer matrix.
[1] S. Harms K. Rätzke, F. Faupel, G. J. Schneider, L. Willner, D. Richter in press Macromolecules 2010