Einfluss der Verarbeitungstechnologie und Werkstoffzusammensetzung auf die Struktur-Eigenschafts-Beziehungen von thermoplastischen Nanoverbundwerkstoffen

Die Einarbeitung von nanoskaligen Füllstoffen zur Steigerung von polymeren Eigenschaftsprofilen ist sehr viel versprechend und stößt daher heutzutage sowohl in der Forschung als auch in der Industrie auf großes Interesse. Bedingt durch ausgeprägte Oberflächen und hohe Anziehungskräfte, liegen Nanopartikel allerdings nicht singulär sondern als Partikelanhäufungen, so genannten Agglomeraten oder Aggregaten, vor. Zur Erzielung der gewünschten Materialverbesserungen gilt es, diese aufzuspalten und homogen in der polymeren Matrix zu verteilen. Bei thermoplastischen Kunststoffen ist die gleichläufige Doppelschneckenextrusion eines der gängigsten Verfahren zur Einarbeitung von Additiven und Füllstoffen. Aus diesem Grund war es Ziel dieser Arbeit, mittels dieses Verfahrens verbesserte Verbundwerkstoffe mit Polyamid 66- und Polyetheretherketon-Matrix, durch Einarbeitung von nanoskaligem Titandioxid (15 und 300 nm), zu generieren. In einem ersten Schritt wurden die verfahrenstechnischen Parameter, wie Drehzahl und Durchsatz, sowie die Prozessführung und damit deren Einfluss auf die Materialeigenschaften beleuchtet. Der spezifische Energieeintrag ist ausschlaggebend zur Deagglomeration der Nanopartikel. Dieser zeigte leichte Abhängigkeiten von der Drehzahl und dem Durchsatz und verursachte bei der Einarbeitung der Partikel keine wesentlichen Unterschiede in der Aufspaltung der Partikel sowie gar keine in den resultierenden mechanischen Eigenschaften. Die Prozessführung wurde unterteilt in Mehrfach- und Einfachextrusion. Die Herstellung eines hochgefüllten Masterbatches, dessen mehrfaches Extrudieren und anschließendes Verdünnen, führte zu einer sehr guten Deagglomeration und stark verbesserten Materialeigenschaften. Mittels Simulation des Extrusionsprozesses konnte festgestellt werden, dass das Vorhandensein von ungeschmolzenem Granulat in der Verfahrenszone zu einer Schmelze/Nanopartikel/ Feststoffreibung führt, die die Ursache für eine sehr gute Aufspaltung der Partikel zu sein scheint. Durch Modifikation des Extrusionsprozesses erreichte die Einfachextrusion annähernd den Grad an Deagglomeration bei Mehrfachextrusion, wobei die Materialien bei letzterem Verfahren die besten Eigenschaftsprofile aufwiesen. In einem zweiten Schritt wurde ein Vergleich der Einflüsse von unterschiedlichen Partikelgrößen und –gehalten auf die polymeren Matrizes vollzogen. Die 15 nm Partikel zeigten signifikant bessere mechanische Ergebnisse auf als die 300 nm Partikel, und die Wirkungsweise des 15 nm Partikels auf Polyetheretherketon war stärker als auf Polyamid 66. Es konnten Steigerungen in Steifigkeit, Festigkeit und Zähigkeit erzielt werden. Rasterelektronenmikroskopische Aufnahmen bestätigten diese Ergebnisse. Eine Berechnung der Plan-Selbstkosten von einem Kilogramm PEEK-Nanoverbundwerkstoff im Vergleich zu einem Kilogramm unverstärktem PEEK verdeutlichte, dass ein Material kreiert wurde, welches deutlich verbesserte Eigenschaften bei gleichem Preis aufweist. Zusammenfassend konnte in dieser Arbeit ein tieferes Verständnis des Extrusionsvorganges zur Herstellung von kostengünstigen und verbesserten Thermoplasten durch das Einbringen von Nanopartikeln gewonnen werden

Sustainable and Selective Monomethylation of Anilines by Methanol with Solid Molecular NHC-Ir Catalysts

Using feedstock methanol as a green methylation reagent, the selective <i>N-</i>monomethylation of anilines is realized under mild reaction conditions by using N-heterocyclic carbene iridium (NHC-Ir) coordination assemblies as highly efficient solid molecular catalysts. Along with a broad substrate scope and good functional group tolerance, up to quantitative yield and 2.0 × 10⁴ turnover numbers (TONs) are obtained even at low catalyst loadings. Notably, the solid NHC-Ir molecular catalyst can be easily recovered and recycled more than 20 times without obvious loss of reactivity and selectivity. Furthermore, this selective practical protocol can be successfully extended to direct methylation of highly functionalized bioactive compounds including 3-aminoestrone, cinacalcet, and their analogues in excellent yields and selectivities, highlighting their potential application in pharmaceuticals

Novel Supramolecular Thixotropic Metallohydrogels Consisting of Rare Metal–Organic Nanoparticles: Synthesis, Characterization, and Mechanism of Aggregation

Even without obvious sticky sites, novel supramolecular thixotropic metallohydrogels consisting of rare metal–organic nanoparticles (MNPs) have been readily accessible from simple structured pincer-type terpyridine Cu­(II) complexes at the gelator concentration as low as 0.25 wt %. The obtained soft materials have been fully characterized by using a combination of experimental techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), X-ray diffraction (XRD), high-resolution mass spectrometry (HR-MS), and rheology measurements. Based on these studies, hypothesized molecular assembly mechanisms for distinctly different morphologies observed in different solvents were proposed. Besides general heating–cooling gel preparation procedures, surprisingly, the metallohydrogel was formed by simply stirring the mixture of pincer ligand and Cu salts in water directly, further indicating thixotropic property and self-healing ability of the resulting metallohydrogel under external stress. This stirring approach is highly anion and phase selective with various potential applications. Furthermore, the infrequent observation of the crystal growth from metallogels <i>in situ</i> readily reavealed the self-assembly mechanism that π-stacking and metal–metal interactions along with hydrogen-bonding interactions between gelator and guest molecules are responsible for the gel formation, which is further confirmed by the control gel collapse experiment via external ligand substitution. All these results indicated that pincer organometallic complexes not only can function as a new type of hydrogelators but also are readily to fabricate useful thixotropic materials with various applicability based on their morphologies and assembly mechanism studies

Highly Efficient Aminocarbonylation of Iodoarenes at Atmospheric Pressure Catalyzed by a Robust Acenaphthoimidazolyidene Allylic Palladium Complex

A robust allylic palladium–NHC complex was developed and exhibited extremely high catalytic activity toward aminocarbonylation of various (hetero)aryl iodides under atmospheric carbon monoxide pressure, in which a broad range of secondary and primary amines were well tolerated. In addition, the concise synthesis of an anticancer drug tamibarotene was accomplished even in a gram scale, further highlighting the practical applicability of the protocol

Robust Acenaphthoimidazolylidene Palladium Complexes: Highly Efficient Catalysts for Suzuki–Miyaura Couplings with Sterically Hindered Substrates

Robust acenaphthoimidazolylidene palladium complexes have been demonstrated as highly efficient and general catalysts for the sterically hindered Suzuki–Miyaura cross-coupling reactions in excellent yields even with low catalyst loadings under mild reaction conditions. The high catalytic activity of these complexes highlights that, besides the “flexible steric bulky” concept, σ-donor properties of the NHC ligands are also crucial to accelerate the transformations

Acenaphthoimidazolylidene Gold Complex-Catalyzed Alkylsulfonylation of Boronic Acids by Potassium Metabisulfite and Alkyl Halides: A Direct and Robust Protocol To Access Sulfones

A robust acenaphthoimidazolylidene gold complex is demonstrated as a highly efficient catalyst in the direct alkylsulfonylation of boronic acids. Remarkably, a wide range of highly reactive and unreactive C-electrophiles were well-tolerated to produce various (hetero)­aryl-alkyl, aryl-alkenyl, and alkenyl-alkyl sulfones in satisfactory yields with 5 mol % catalyst loading. Along with the steric properties of NHC ligands, the high catalytic activity of this gold complex suggests that the strong σ-donation of acenaphthoimidazolylidene also played a role in promoting this challenging redox-neutral catalytic process

Macroscopic and Fluorescent Discrimination of Adenosine Triphosphate via Selective Metallo-hydrogel Formation: A Visual, Practical, and Reliable Rehearsal toward Cellular Imaging

With use of simple terpyridine zinc nitrate complexes, intriguing visual recognition of adenosine triphosphate (ATP) via selective coordination assembly leading to two-component metallo-hydrogel formation has been realized. With intensive fluorescent study and density functional theory calculations, it may be inferred, besides the selective metal–ligand interaction between Zn center and phosphate groups, the intramolecular π-stacking between the planar nucleobases of ATP and the metal-hybrid aromatic ring of pincer complex strongly affected the geometry of the coordinated adducts and possible molecular self-assembly process, which constitute a completely new sensing strategy in comparison with the conventional approaches. Furthermore, in light of extreme sensitivity of pincer zinc complexes toward ATP at micromolar scale (1.85 μM) and remarkable fluorescent enhancement (ca. 44-fold) upon ATP addition, the feasibility of the low cytotoxicity pincer zinc complexes in monitoring ATP in HeLa cells has been fulfilled with confocal fluorescence microscopy

CD146 Deletion in the Nervous System Impairs Appetite, Locomotor Activity and Spatial Learning in Mice

<div><p>Cell adhesion molecules (CAMs) are crucial effectors for the development and maintenance of the nervous system. Mutations in human CAM genes are linked to brain disorders and psychological diseases, and CAM knockout mice always exhibit similar behavioral abnormalities. CD146 is a CAM of the immunoglobulin superfamily that interacts with Neurite Outgrowth Factor and involved in neurite extension <i>in vitro</i>. However, little is known about its <i>in vivo</i> function in the nervous system. In this study, we used a murine CD146 nervous system knockout (CD146^ns-ko) model. We found that the brains of some CD146^ns-ko mice were malformed with small olfactory bulbs. CD146^ns-ko mice exhibited lower body weights and smaller food intake when compared with wild type littermates. Importantly, behavior tests revealed that CD146^ns-ko mice exhibited significant decreased locomotor activity and impaired capacity for spatial learning and memory. Our results demonstrate that CD146 is important for mammalian nervous system development and proper behavior patterns.</p></div

CaMKIIβ KO mice have impaired cognitive function and nesting behavior.

<p>(<b>A</b>) None of the mice show a preference for two identical objects presented in the NOR training session. In the subsequent test session done after a 4 hour delay, the WT mice showed a preference for the novel object as indicated by increased D2 index, but the KO mice showed no preference for either object. (<b>B</b>) CaMKIIβ KO mice made a significantly lower quality nest compared to their littermates. (<b>C</b>) Representative photographs of the nests. Photographs on the bottom row are higher-power views of the nests at 24 h. *p<0.05, **p<0.01. Data are presented as means ±SEM. Number of mice per group is indicated on each graph.</p

Knockout of CD146 in the nervous system resulted in decreased locomotor activity in mice.

<p>(A) Mice at the ages of 1 month and 3 months were subjected to the Rotarod test. Falling latency was recorded with a 30 seconds cut-off time. Mice at the ages of 1 month, 3 months and 6 months were subjected to the open field test. Representative running tracks of mice at the age of 3 months were shown (B). B: begin-point. E: end-point. During the 5-min free running, distance travelled (C), maximum speed (D) and rest time (E) of WT and CD146^ns-ko mice were recorded and analyzed with a two-way ANOVA. Data is presented as means ± SEM.</p