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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Crystallization, Nucleation and Self-Assembly

CPP 19.5: Vortrag

Dienstag, 28. März 2023, 10:45–11:00, MER 02

How entanglements determine the morphology of semicrystalline polymers — Zefan Wang, Mareen Schaller, Albrecht Petzold, Kay Saalwächter, and •Thomas Thurn-Albrecht — Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06099 Halle

Crystallization of polymers from entangled melts generally leads to the formation of semicrystalline materials with a nanoscopic lamellar morphology. Controlling this structure is key to the rational design of thermoplastic materials, but there is no consensus yet on the factors that control the thickness of the amorphous layers and therefore together with the crystal thickness the crystallinity. We here elucidate the effect of entanglements on the morphology in a series of model blends of high-molecular-weight polymers with unentangled oligomers leading to a reduced entanglement density in the melt as characterized by rheological measurements. Small-angle X-ray scattering experiments after isothermal crystallization reveal a reduced thickness of the amorphous layers, while the crystal thickness remains largely unaffected. A simple yet quantitative model without adjustable parameter is suggested, according to which the measured thickness of the amorphous layers adjusts itself in such a way that the entanglement concentration reaches a specific maximum value.