Regensburg 2004 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Chemische Physik und Polymerphysik
CPP 7: Physics of Polymers I
CPP 7.1: Vortrag
Montag, 8. März 2004, 14:00–14:15, H 37
Scaling properties of critical polymer blends and polymer solutions near the glass transition — •Werner Köhler, Wolfgang Enge, and Jürgen Rauch — Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth
Critical polymer blends show Ising-like critical scaling close to Tc and mean-field behavior for larger є = (T − Tc)/Tc. Because of the thermal activation of the Onsager coefficient, however, the critical exponent γ cannot be directly observed in the temperature dependence of the diffusion coefficient D within the mean-field regime. Similarly, the diffusion coefficient of semidilute and concentrated polymer solutions typically only approaches the concentration scaling law but then rapidly decreases because of the increasing glass temperature of the solution. Contrary to D, the Soret coefficient ST is neither sensitive to thermal activation of the Onsager coefficient nor to the increase of local friction at the glass transition and shows clean scaling in both cases. Experiments have been performed on semidilute and concentrated solutions of polystyrene in toluene and on critical poly(dimethylsiloxane)/poly(ethyl-methylsiloxane) mixtures.