Regensburg 2002 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 7: Struktur und Dynamik in Polymersystemen II
CPP 7.2: Vortrag
Montag, 11. März 2002, 15:20–15:40, H38
Behavior of polymers confined to nanoporoues glasses studied by dielectric, thermal and vibrational spectroscopy: Cut - off length scale for glass transition ? — •Schoenhals Andreas1, Goering Harald1, Brzezinka Klaus1, and Schick Christoph2 — 1Bundesanstalt fuer Materialforschung und -pruefung, Unter den Eichen 87, D-12205 Berlin — 2Universitaet Rostock, Fachbereich Physik, Universitaetsplatz 3, D-18051 Rostock
Dielectric spectroscopy, temperature modulated DSC experiments and Polarized Raman scattering are employed to study the molecular dynamics of oligomeric poly(propylene glycol) (PPG) and poly(dimethyl siloxane) (PDMS) melts confined to nanoporous glasses (pore sizes 2.5, 5.0, 7.5 and 20 nm). The relaxation times obtained by both methods correlate directly to each other. The change of the temperature dependence of the relaxation times compared to bulk state depends on the pore size. For large pore sizes an acceleration up of the segmental dynamics compared to the bulk state is observed which is already known for low molecular glass forming liquids. For smaller pore sizes the molecular dynamics is slower than in the bulk. The observed behavior is nearly independent of the molar mass of the polymer and of the treatment of internal glass surfaces. The experimental results are discussed in the frame of an interplay of confinement and adsorption effects. Moreover a length scale as lower bound for the glass transition is estimated in the range from 1.5 nm to 5 nm depending on the structure of the investigated polymer.