Regensburg 2002 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 12: Poster: Polymere Netzwerke, Blends und Blockcopolymere

CPP 12.5: Poster

Wednesday, March 13, 2002, 16:30–18:00, B

Coupling between temperature and concentration in a polymer blend in the vicinity of a consolute critical point — •Wolfgang Enge and Werner Köhler — Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth, Germany

The polymer blend polyethyleneglycol/polypropyleneglycol (PEG600/ PPG1000) was studied by the transient holographic grating technique of Thermal Diffusion Forced Rayleigh Scattering near the critical point in the one-phase regime. The time-dependence of the temperature-induced concentration grating yields the mutual diffusion coefficient D which vanishes at the critical point (critical slowing down). The amplitude of the observed concentration grating is proportional to the Soret coefficient S_T = D_T/D, D_T being the thermal diffusion coefficient. On approach of the critical point, we observe a divergence of the induced concentration modulation due to the critical slowing down of D. D_T is insensitive to the critical point and remains almost constant.