Bayreuth 1998 – wissenschaftliches Programm

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PO: Polymerphysik

PO 8: Poster: Phasenumwandlungen

PO 8.3: Poster

Mittwoch, 11. März 1998, 15:25–17:15, P1

Comparison of Ultrasonic and Conventional Rheology during Crystallization and Melting in Bulk Poly(ethylene oxide) and in the Triblock Copolymer with Polystyrene — •I. Alig¹, S. Tadjbakhsch¹, G. Floudas², and C. Tsitsilianis³ — ¹Deutsches Kunststoff-Institut, Schlossgartenstrasse 6, D-64289 Darmstadt — ²Foundation of Research and Technology-Hellas, 71110 Heraklion, Greece — ³Department of Chemical Engineering, University of Patras, 26500 Patras, Greece

We report a combined study using an ultrasonic shear wave reflection technique and conventional low-frequency rheology for the investigation of the crystallization kinetics and the melting of a poly(ethylene oxide) (PEO) homopolymer and a poly(ethylene oxide) - polystyrene - poly(ethylene oxide) (PEO-PS-PEO) triblock copolymer. Isothermal and isochronal measurements of the complex dynamic shear modulus have been performed with the ultrasonic shear wave reflection method (f=3.5MHz) and conventional rheology (f=0.16Hz). The system was regarded as a composite material made of spherulites within the amorphous matrix. In contrast to the ultrasonic experiments the isothermal rheological experiments could not be described by a simple combination of a mixing law for the modulus and the Avrami equation. This is explained by shear induced crystallization and/or different coupling of the macroscopic shear in the conventional rheology. For the copolymer a kinetic frustration of the crystallization by the glassy PS-microphase was found.