Dresden 2009 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 21: Polymer Physics II
CPP 21.3: Vortrag
Mittwoch, 25. März 2009, 10:00–10:15, ZEU 114
Molecular weight dependence of the crystalline-amorphous superstructure of semi-crystalline polymers — •Albrecht Petzold and Thomas Thurn-Albrecht — Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle, Germany
During crystallization polymers form a crystalline-amorphous superstructure consisting of lamellar crystals with a typical thickness of about 10 nm. This non-equilibrium structure is often explained by the kinetics of crystallization during which the crystals which form fastest, are selected. The thickness da of the amorphous layers separating adjacent crystals is in most cases not considered. To find out which parameters and physical processes determine da, we undertook a systematic study of the corresponding structural parameters by small angle x-ray scattering using a series of polyethyleneoxide (PEO) with different molecular weight as a model system. We show that for this system the thickness of the amorphous layers is a well defined equilibrium quantity which depends only on molecular weight and temperature, and not on the conditions of crystallization, while the thickness of the crystalline layers is strongly influenced by the kinetics of crystallization and lamellar thickening and in general is much less uniform. The fact that da increasing with molecular weight indicates that the semi-crystalline morphology is related to structure of the chains in the amorphous melt before crystallization.