Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 40: Polymer Crystallization and Semicrystalline Polymers

CPP 40.3: Vortrag

Donnerstag, 17. März 2011, 11:15–11:30, ZEU 160

Melt dynamics and semi-crystalline structure of polyethyleneoxide — •Albrecht Petzold and Thomas Thurn-Albrecht — Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle (Saale)

During crystallization polymers form a crystalline-amorphous superstructure consisting of lamellar crystals with a typical thickness of about 10nm. This non-equilibrium structure is often explained by the kinetics of crystallization during which the crystals which form fastest, are selected. The thickness d_a of the amorphous layers separating adjacent crystals is in most cases not considered. To find out which parameters and physical processes determine d_a, 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 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 semi-crystalline morphology is related to the structure of the chains in the amorphous melt before crystallization. For fast crystallization the coiled structure remains almost unchainged during crystallization and frozen topological defects limits the crystal size. When there is enough time for reorganization the crystal thickness exceeds the size of the coil in the melt and the crystal thickness is maximised.