Publikationen

Hierarchical assembly architectures of functional polymer particles are promising because of their physicochemical and surface properties for multi-labeling and sensing to catalysis and biomedical applications. While polymer nanoparticles' interior is mainly made up of the cross-linked network, their surface can be tailored with soft, flexible, and responsive molecules and macromolecules as potential support for the controlled particulate assemblies. Molecular surfactants and polyelectrolytes as interfacial agents improve the stability of the nanoparticles whereas swellable and soft shell-like cross-linked polymeric layer at the interface can significantly enhance the uptake of guest nano-constituents during assemblies. Besides, layer-by-layer surface-functionalization holds the ability to provide a high variability in assembly architectures of different interfacial properties. Considering these aspects, various assembly architectures of polymer nanoparticles of tunable size, shapes, morphology, and tailored interfaces together with controllable interfacial interactions are constructed here. The microfluidic-mediated platform has been used for the synthesis of constituents polymer nanoparticles of various structural and interfacial properties, and their assemblies are conducted in batch or flow conditions. The assemblies presented in this progress report is divided into three main categories: cross-linked polymeric network's fusion-based self-assembly, electrostatic-driven assemblies, and assembly formed by encapsulating smaller nanoparticles into larger microparticles.

The presence of the polycationic macromolecule poly(diallyldimethylammonium chloride) (poly-DADMAC) has a strong effect on the shape and size of colloidal gold nanoparticles formed by the reduction of tetrachloroauric acid with ascorbic acid in aqueous solution. It slows down nanoparticle growth and supports the formation of nonspherical, partially highly fractal and hierarchical nanoparticle shapes. Four structural levels have been recognized from the near-spherical gold nanoparticles in the lower nanometer range over compact aggregates in the midnanometer range and flower and star-like particles in the submicron range up to larger filamentous aggregates. High-contrast scanning electron microscope (SEM) images show that single gold nanoparticles and clusters of them are connected by bundles of macromolecules in large aggregates. The investigation showed that a large spectrum of different nanoparticle shapes and sizes can be accessed by tuning the poly-DADMAC concentrations and their ratio to other reactants. The nanoassemblies with a very high specific surface area might be of interest for SERS and heterogeneous catalysis.

Rauchende Salpetersäure ist im Handel nur hochrein zu kaufen und daher teuer - zu teuer für Hochschulpraktika. An der TU Ilmenau synthetisieren die Studierenden die HNO3 nun selbst als Praktikumsversuch und nutzen dafür historische Anleitungen.

Bioactive composite material based on hydroxyapatite (HA), sodium alginate (Alg) with different content of graphene oxide (GO) was synthesized by the wet chemistry method and characterized by TEM, XRD, FTIR, HPLC analysis. Introduced the GO nanoparticles, as well as Ca2+ ions, as cross-linker of Alg macromolecules by the beads formation, lead to enhancement of the composites mechanical properties. HA-Alg-GO10 sample with GO content of 0.004% in relation to the HA powder has a much higher Youngs modulus (1325 MPa) in comparison with GO-free HA-Alg composite (793 MPa), as well as steel sample of the same size (˜706 MPa). The addition of GO reduces the degree of the composites swelling in a phosphate buffered saline for 43% and enhances the beads shape stability. Chlorhexidine bigluconate release from GO containing samples lasts for 48 h longer according to HPLC study. The findings clear demonstrate the potential possibility of applications of the HA-Alg-GO composite material in bioengineering of bone tissue to fill bone defects of various geometries with the function of prolonged release of the drug. It is assumed that HA-Alg-GO composite material can be used in 3D modeling of areas of bone tissue that have to bear a mechanical load.

Particulate polymers at the nanoscale are exceedingly promising for diversified functional applications ranging from biomedical and energy to sensing, labeling, and catalysis. Tailored structural features (i.e., size, shape, morphology, internal softness, interior cross-linking, etc.) determine polymer nanoparticles' impact on the cargo loading capacity and controlled/sustained release, possibility of endocytosis, degradability, and photostability. The designed interfacial features, however (i.e., stimuli-responsive surfaces, wrinkling, surface porosity, shell-layer swellability, layer-by-layer surface functionalization, surface charge, etc.), regulate nanoparticles interfacial interactions, controlled assembly, movement and collision, and compatibility with the surroundings (e.g., solvent and biological environments). These features define nanoparticles' overall properties/functions on the basis of homogeneity, stability, interfacial tension, and minimization of the surface energy barrier. Lowering of the resultant outcomes is directly influenced by inhomogeneity in the structural and interfacial design through the structure-function relationship. Therefore, a key requirement is to produce well-defined polymer nanoparticles with controlled characteristics. Polymers are amorphous, flexible, and soft, and hence controlling their structural/interfacial features through the single-step process is a challenge. The microfluidics reaction strategy is very promising because of its wide range of advantages such as efficient reactant mixing and fast phase transfer. Overall, this feature article highlights the state-of-the-art synthetic features of polymer nanoparticles with perspectives on their advanced applications.