Regensburg 2019 – wissenschaftliches Programm
CPP 10.1: Vortrag
Montag, 1. April 2019, 15:00–15:15, H13
The Underestimated Effect of Intracrystalline Chain Dynamics on the Morphology and Stability of Semicrystalline Polymers — •Martha Schulz, Anne Seidlitz, Ricardo Kurz, Ruth Bärenwald, Albrecht Petzold, Kay Saalwächter, and Thomas Thurn-Albrecht — Martin-Luther-Universität Halle-Wittenberg
Some polymers show translational motion of the chains in crystallites - the αc-relaxation. Although it was recognized early by BOYD that αc-mobile polymers have a higher crystallinity than crystal-fixed polymers, the relaxation process has been ignored in most crystallization models. We show that the αc-relaxation has a strong influence on the crystallization process, changing morphology and stability of the semicrystalline structure. Using SAXS, we compare structural characteristics for PEO (αc -mobile) and PCL (crystal-fixed) after isothermal crystallization and during heating. With NMR we can estimate the timescale of the αc-relaxation depending on Tc. A direct comparison points out fundamental differences: PCL shows marginally stable lamellae with a narrow thickness distribution, starting to reorganize for T>Tc. In contrast, PEO shows a well-defined, narrowly distributed amorphous thickness da and a broad thickness distribution of the lamellae. For T>Tc, the lamellae are stable over a wide range. We hypothesize that due to the αc-relaxation, the lamellae thicken directly behind the growth front up to a minimal da. This is supported by NMR-results: At high Tc the αc-relaxation is fast enough to enable crystal reorganization to take place in a narrow zone directly behind the growth front.
Schulz, M.; Macromolecules 51, 8377 (2018)