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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 14: Crystallization, Nucleation and Self Assembly I

CPP 14.4: Talk

Tuesday, March 12, 2013, 10:15–10:30, H39

Effect of the Crystalline α_c-Process on the Morphology of Semicrystalline Polymers: a Comparative SAXS- Study on Poly-є-Caprolactone and Polyethyleneoxide — Anne Seidlitz, Thomas Thurn-Albrecht, •Ruth Bärenwald, and Kay Saalwächter — MLU Halle-Wittenberg, 06120 Halle (Saale)

Semi-crystalline polymers can be classified into two different types, depending on the presence (α_c-mobile) or absence (crystal-fixed) of the α_c-relaxation, which provides mobility to the chains in the crystals. Starting from a hypothesis of Boyd, that all polymers with a high crystallinity are α_c-mobile while all polymers with a low crystallinity are crystal-fixed, we investigated the morphology of polyethyleneoxide as a polymer with mobile crystalline chains and poly-є-caprolactone as a polymer with fixed chains. We performed small-angle X-ray scattering experiments and developed a simulation based on the paracrystalline model to derive quantitative morphological information from the SAXS data. Clear differences between the structure of PEO and PCL were observed. For PCL the crystalline thickness d_c is well defined, while the amorphous thickness d_a displays a broad distribution. PEO shows a small, well defined d_a and a broad thickness distribution of the crystalline lamellae.This confirms a different mode of structure formation. The crystalline lamellae in PEO, where thickening begins already at the growth front, can reorganize during crystallization until a minimal d_a, possibly reflecting a locally equilibrated entanglement structure, is established. For PCL no thickening of the initially formed lamellae is possible and the amorphous parts are randomly filled.