Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 20: POSTER A

CPP 20.8: Poster

Montag, 24. März 2003, 19:00–21:00, ZEU/250

Thermal diffusion, heat and mass transport in semidilute and concentrated polymer solutions in the vicinity of the glass transition — •Jürgen Rauch and Werner Köhler — Physikalisches Institut, Universität Bayreuth, 95445 Bayreuth, Germany

Solutions of polystyrene in toluene from oligomers (M_W=370 g/mol) up the high molecular weights (M_W= 4000 kg/mol) have been investigated over a broad concentration range from dilute to concentrated. The corresponding dynamic range extends from the fast dynamics of the liquid state to the slow dynamics of the glassy state. The thermal diffusion coefficient D_T, the mutual mass diffusion coefficient D, and the Soret coefficient S_T were determined by a transient holographic grating technique and, in the case of D, also by photon correlation spectroscopy. An Ansatz will be suggested to distinguish between thermodynamic and frictional contributions to S_T and D_T. The concentration dependence of D_T can directly be related to the self diffusion coeffiecient D_s,tol of the solvent molecules. The molecular weight independce of D_T, which is well-established in the literature for dilute polymer solutions, breaks down in the concentrated regime.