Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 1: Polymerschmelzen

CPP 1.6: Vortrag

Montag, 24. März 2003, 11:15–11:30, ZEU/160

Coupling between temperature and concentration in a polymer blend near a consolute critical point — •Wolfgang Enge and Werner Köhler — Physikalisches Institut, Universität Bayreuth, 95445 Bayreuth, Germany

We have used a holographic grating technique with a small q-vector (10⁴ cm⁻¹) to study the binary polymer blend poly(dimethylsiloxane)/poly(ethylmethylsiloxane) near the consolute critical point in the one-phase region. For the first time, to our knowledge, the Soret coefficient S_T and the thermal diffusion coefficient D_T were quantitatively determined for a polymer blend. We observe the well known critical slowing down of the mutual diffusion coefficient D. D_T decreases with decreasing temperature, but it appears insensitive to the critical point and does not show critical enhancement. As a consequence, the Soret coefficient S_T = D_T/D diverges on approach of the critical point. These experiments are complemented with measurements on samples with off-critical composition.