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PO: Polymerphysik

PO 8: Poster: Polymermischungen und Copolymere

PO 8.5: Poster

Tuesday, March 2, 1999, 14:00–16:00, Foyer

Composition fluctuations in a binary polymer blend in the one- and two-phase region studied by static and dynamic light scattering: Comparison between critical and non-critical composition — •S. Eckert and I. Alig — Deutsches Kunststoff-Institut, Schloßgartenstr. 6, D-64289 Darmstadt

A critical and a non-critical mixture of polyethylene glycol and polypropylene glycol were investigated by static and dynamic light scattering in the one-phase region and in the two-phase region in both coexisting phases. The critical exponents and amplitudes of the correlation length and the mutual diffusion coefficient were determined. For the critical mixture, the results for the one-phase region are consistent with the 3d-Ising model, while in the two-phase region, the critical exponents showed a tendency to mean field behavior. The data of the non-critical mixture, analyzed in the framework of a pseudo-spinodal concept, revealed mean field behavior in the one-phase- and in the two-phase region. The coexistence curves for both mixtures were determined by differential refractometry. The critical exponent of the order parameter, determined from the coexistence curve of the critical mixture, showed Ising-like behavior, whereas the non-critical mixture is represented by a mean field exponent. There is an indication for a different scaling behavior between the order parameter on one side and the correlation length and the diffusion coefficient on the other side.