Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Poster Session I

CPP 20.33: Poster

Monday, March 12, 2018, 17:30–19:30, Poster A

Evaluating thermal diffusion forced rayleigh scattering experiments with polydisperse polymers — •Bastian Pur and Werner Köhler — Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth, Germany

The Soret effect (thermophoresis) describes a diffusion flux that is driven by a temperature gradient in a multicomponent mixture. By means of thermal diffusion forced rayleigh scattering (TDFRS), which is a holographic grating technique, one can obtain the collective (Fickian) diffusion coefficient D, the thermal diffusivity D_th, the Soret coefficient S_T and the thermal diffusion coeffcient, also known as the thermophoretic mobility, D_T. Measurements with binary mixtures, e.g. polymer solutions, can be evaluated with an working equation deduced from the linear response theory. This works well for monodispers polymers, but there are discrepancies due to polydispersity. Polydispersity was obtained by dynamic light scattering experiments, which yields the hydrodynamic radii distribution. From the initial rise of the concentration signal of TDFRS measurements, we can calculate the thermal diffusion coefficient D_T, even for polydisperse polymers.