Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 15: POSTER: Polymers and Biomaterials

CPP 15.31: Poster

Tuesday, March 9, 2004, 17:00–19:00, B

Evidence of pre-order in polymer melts revealed from dielectric spectroscopy — •Andreas Wurm, Ragab Soliman, and Christoph Schick — Universität Rostock, Fachbereich Physik, Universitätsplatz 3, 18051 Rostock

Existence and formation of pre-ordered structures as the initial step of polymer crystallization are discussed controversially. Most of the findings and interpretations are based on scattering experiments, which test small density differences between the assumed precursors of the crystals and the surrounding melt. Because of the low contrast the interpretation of experimental results becomes often speculative. Contrary relaxation experiments are probing motions in the sample and are therefore independent on density contrast. During crystallization material is transformed from the liquid to the solid state. Consequently, motions (fluctuations) typical for a liquid become impossible and do not longer contribute to the measured relaxing signal. For pre-ordered structures we expect some decrease in mobility too because of the changes in conformation on pre-ordering. On the other hand due to the formation of regions with different order new internal surfaces will be formed. At such surfaces Maxwell-Wagner-Sillars charge carrier relaxation may occur and contribute to the measured dielectric signal.

We have studied the complex dielectric permittivity of polycaprolactone (PCL) and polypropylene (sPP) during non-isothermal and isothermal crystallization in the frequency range from 0.01 Hz to 10 MHz.