The structure formation of melt-crystallized semicrystalline polymers strongly depends on the interplay of the different dynamics in the crystalline and amorphous phases and the kinetics during the growth of the crystallites. Here, the decisive role of intracrystalline chain mobility, the so-called αc-relaxation, and the effect of entanglements onthe morphology is addressed. The connections between structure formation and dynamics of polymer chains are presented on the example of two model polymers with and without αc-relaxation: Poly(ethylene oxide) (PEO) [1] and poly(ε-caprolactone) (PCL) [2] which are investigated with small-angle X-ray scattering (SAXS) and NMR spectroscopy, respectively. The morphology of PCL has, in agreement with classical crystallization theories, a well-defined crystalline thickness. In PEO the intra-crystalline mobility causes a thickening of the crystalline lamellea which leads subsequently to a minimization and formation of a well-defined amorphous thickness. NMR analysis reveals that the crystal reorganization occurs on the same time scale as the crystal growth itself. The analysis of poly(oxymethylene) (POM), which exhibits a comparably slow αc-relaxation, enables the separate investigation of crystal reorganization and crystal growth on the morphology. Further investigations address the relationship between morphology and entangled dynamics in the amorphous phase and the melt. The addition of short chains from the same species prior to crystallization reduces the entanglement density in the melt and allows us to study the topological restrictions of entanglements and the influence on the structure formation, while all other parameters are kept constant.

NMR investigations of dynamics in the different phases of semicrystalline polymers

255th National Meeting (2018)

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