Solid-state creep, ductility, and drawability are relevant mechanical properties of "crystal-mobile" polymers, related to a large-scale chain transport through the crystal, which is in turn mediated by intracrystalline monomer jumps. Here, high-M w poly(ethylene oxide) is used as a well-controlled model system, modulating the properties of the amorphous phase by diluting with a non-crystallized oligomer. Faster intracrystalline motions are found upon oligomer addition, indicating little changes in the fold surface and a dominant influence of the somewhat reduced lamellar thickness.
Neuromelanin-sensitive MRI receives interest as potential biomarker in neurodegenerative diseases, such as Parkinson’s and Alzheimer’s disease. It is known that human neuromelanin pigments bind large quantities of toxic metal ions, especially iron but also other transition metals including copper. These melanin-iron complexes are a potential source of paramagnetic relaxation enhancement of water proton. In relaxometry investigations, we found deviations from a simple linear concentration-dependent T1 shortening in synthetic neuromelanins containing different amounts of iron and copper. Knowledge of the occupation of distinct metal binding sites seems crucial for contrast optimization or attempts to quantify metal content by MRI.
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