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Author: Kickelbick, Guido × End date: 2024 × Start date: 2020 × DDC: 540 × Has files: Yes × Type: Text × Publisher: Basel : MDPI × WGL Institute: INM ×

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    Self-Healing Iron Oxide Polyelectrolyte Nanocomposites: Influence of Particle Agglomeration and Water on Mechanical Properties
    (Basel : MDPI, 2023) Oberhausen, Bastian; Plohl, Ajda; Niebuur, Bart-Jan; Diebels, Stefan; Jung, Anne; Kraus, Tobias; Kickelbick, Guido
    Self-healing nanocomposites can be generated by organic functionalization of inorganic nanoparticles and complementary functionalization of the polymer matrix, allowing reversible interactions between the two components. Here, we report on self-healing nanocomposites based on ionic interactions between anionic copolymers consisting of di(ethylene glycol) methyl ether methacrylate, sodium 4-(methacryloyloxy)butan-1-sulfonate, and cationically functionalized iron oxide nanoparticles. The materials exhibited hygroscopic behavior. At water contents < 6%, the shear modulus was reduced by up to 90%. The nanoparticle concentration was identified as a second factor strongly influencing the mechanical properties of the materials. Backscattered scanning electron microscopy and small-angle X-ray scattering measurements showed the formation of agglomerates in the size range of 100 nm to a few µm in diameter, independent of concentration, resulting in the disordering of the semi-crystalline ionic polymer blocks. These effects resulted in an increase in the shear modulus of the composite from 3.7 MPa to 5.6 MPa, 6.3 Mpa, and 7.5 MPa for 2, 10, and 20 wt% particles, respectively. Temperature-induced self-healing was possible for all composites investigated. However, only 36% of the maximum stress could be recovered in systems with a low nanoparticle content, whereas the original properties were largely restored (>85%) at higher particle contents.
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    Chemical and Structural Comparison of Different Commercial Food Supplements for Silicon Uptake
    (Basel : MDPI, 2023) Curto, Yannic; Koch, Marcus; Kickelbick, Guido
    Various food supplements for silicon uptake were compared in terms of their structures and chemical compositions. In particular, we analyzed the silanol group content, which can be an indicator of the uptake of the siliceous species in the human body. We analyzed the commercial products Original Silicea Balsam®, Flügge Siliceous Earth Powder, Pure Colloidal Silicon, and BioSil® by applying various methods such as FTIR, 29Si NMR, and TGA. The Si-OH group content of the samples containing pure silica was the highest for the Original Silicea Balsam followed by the Pure Colloidal Silicon. The siliceous earth powder revealed the lowest content of such groups and the densest structure. BioSil® contained a considerable concentration of organic molecules that stabilized orthosilicic acid. The study may help to understand the silicon uptake behavior of different food supplements depending on their chemical structure.