Publikationen

The development of hierarchically porous block copolymer (BCP) membranes via the application of the self-assembly and non-solvent induced phase separation (SNIPS) process is one important achievement in BCP science in the last decades. In this work, we present the synthesis of polyacrylonitrile-containing amphiphilic BCPs and their unique microphase separation capability, as well as their applicability for the SNIPS process leading to isoporous integral asymmetric membranes. Poly(styrene-co-acrylonitrile)-b-poly(2-hydroxyethyl methacrylate)s (PSAN-b-PHEMA) are synthesized via a two-step atom transfer radical polymerization (ATRP) procedure rendering PSAN copolymers and BCPs with overall molar masses of up to 82 kDa while maintaining low dispersity index values in the range of Đ = 1.13–1.25. The polymers are characterized using size-exclusion chromatography (SEC) and NMR spectroscopy. Self-assembly capabilities in the bulk state are examined using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) measurements. The fabrication of isoporous integral asymmetric membranes is investigated, and membranes are examined by scanning electron microscopy (SEM). The introduction of acrylonitrile moieties within the membrane matrix could improve the membranes’ mechanical properties, which was confirmed by nanomechanical analysis using atomic force microscopy (AFM).

The fabrication of nanocomposites containing magnetic nanoparticles is gaining interest as a model for application in small electronic devices. The self-assembly of block copolymers (BCPs) makes these materials ideal for use as a soft matrix to support the structural ordering of the nanoparticles. In this work, a high-molecular-weight polystyrene-b-poly(methyl methacrylate) block copolymer (PSb-PMMA) was synthesized through anionic polymerization. The influence of the addition of different ratios of PMMA-coated FePt nanoparticles (NPs) on the self-assembled morphology was investigated using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The selfassembly of the NPs inside the PMMA phase at low particle concentrations was analyzed statistically, and the negative effect of higher particle ratios on the lamellar BCP morphology became visible. The placement of the NPs inside the PMMA phase was also compared to theoretical descriptions. The magnetic addressability of the FePt nanoparticles inside the nanocomposite films was finally analyzed using bimodal magnetic force microscopy and proved the magnetic nature of the nanoparticles inside the microphase-separated BCP films.

Abstract Block copolymers (BCPs) in the bulk state are known to self-assemble into different morphologies depending on their polymer segment ratio. For polymers with amorphous and crystalline BCP segments, the crystallization process can be influenced significantly by the corresponding bulk morphology. Herein, the synthesis of the amorphous-crystalline BCP poly(dimethyl silacyclobutane)-block-poly(2vinyl pyridine), (PDMSB-b-P2VP), by living anionic polymerization is reported. Polymers with overall molar masses ranging from 17 400 g to 592 200 g mol−1 and PDMSB contents of 4.8–83.9 vol% are synthesized and characterized by size-exclusion chromatography and NMR spectroscopy. The bulk morphology of the obtained polymers is investigated by means of transmission electron microscopy and small angle X-ray scattering, revealing a plethora of self-assembled structures, providing confined and nonconfined conditions. Subsequently, the influence of the previously determined morphologies and their resulting confinement on the crystallinity and crystallization behavior of PDMSB is analyzed via differential scanning calorimetry and powder X-ray diffraction. Here, fractionated crystallization and supercooling effects are observable as well as different diffraction patterns of the PDMSB crystallites for confined and nonconfined domains.

The annual International Day of Women and Girls in Science promotes full and equal access to and participation in science. (1) A focal point for 11 February 2023 is the role of Women and Girls in Science as related to the United Nations sustainable development goals in order to strengthen ties between science, policy, and society. These goals and linking strategies are absolutely central to the field of toxicology! Research published in Chemical Research in Toxicology is an enabling basis for improving many areas of a sustainable future including good health, clean water, and responsible consumption and production. The community of Chemical Toxicologists also contributes to advancing goals for quality education, economic growth, global partnerships, and, relevant in particular with the current initiative, gender equality.

Human respiratory mucus is a biological hydrogel that forms a protective barrier for the underlying epithelium. Modulation of the mucus layer has been employed as a strategy to enhance transmucosal drug carrier transport. However, a drawback of this strategy is a potential reduction of the mucus barrier properties, in particular in situations with an increased exposure to particles. In this study, we investigated the impact of mucus modulation on its protective role. In vitro mucus was produced by Calu-3 cells, cultivated at the air-liquid interface for 21 days and used for further testing as formed on top of the cells. Analysis of confocal 3D imaging data revealed that after 21 days Calu-3 cells secrete a mucus layer with a thickness of 24 ± 6 μm. Mucus appeared to restrict penetration of 500 nm carboxyl-modified polystyrene particles to the upper 5–10 μm of the layer. Furthermore, a mucus modulation protocol using aerosolized N-acetylcysteine (NAC) was developed. This treatment enhanced the penetration of particles through the mucus down to deeper layers by means of the mucolytic action of NAC. These findings were supported by cytotoxicity data, indicating that intact mucus protects the underlying epithelium from particle-induced effects on membrane integrity. The impact of NAC treatment on the protective properties of mucus was probed by using 50 and 100 nm amine-modified and 50 nm carboxyl-modified polystyrene nanoparticles, respectively. Cytotoxicity was only induced by the amine-modified particles in combination with NAC treatment, implying a reduced protective function of modulated mucus. Overall, our data emphasize the importance of integrating an assessment of the protective function of mucus into the development of therapy approaches involving mucus modulation.

We report the synthesis of AgNP@PEDOT:PSS hybrid conductive particles with silver cores and polythiophene shells that can be used to formulate sinter-free inks for printing electronics. First, Ag nanocrystals capped with the weakly bound ligand aminohexanoic acid (ε-Ahx) are prepared. The ligand shell is exchanged by reacting the dispersion with the polymer ionomer mixture poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS). The particles are characterized by electron microscopy, dynamic light scattering, Z potential, and Raman spectroscopy, confirming the replacement of the ligands on the metal particle surface. The resulting dispersion is colloidally stable as confirmed by DLS. Inks with a solid content of the hybrid particles of 300 mg mL−1 were prepared and deposited on different substrates. The new particles are components for hybrid inks that become electrically conductive without any chemical or thermal post-deposition treatment. We show that silver-based hybrid inks can be deposited on different substrates and possess an average conductivity after 24 h of drying at room temperature of 1.726 × 106 S m−1 ± 0.326 × 106 S m−1, only one order of magnitude lower than elemental silver and within the same order of magnitude as their gold ink counterpart.

We report on the unusual, advantageous ageing of flexible transparent electrodes (FTEs) that were self-assembled from oleylamine-capped gold nanospheres (AuNPs) by direct nanoimprinting of inks with different particle concentrations (cAu = 3 mg mL−1 to 30 mg mL−1). The resulting lines were less than 2.5 μm wide and consisted of disordered particle assemblies. Small-Angle X-ray Scattering confirmed that particle packing did not change with ink concentration. Plasma sintering converted the printed structures into lines with a thin, electrically conductive metal shell and a less conductive hybrid core. We studied the opto-electronic performance directly after plasma sintering and after fourteen days of storage at 22 °C and 55% rH in the dark. The mean optical transmittance [T with combining macron]400–800 in the range from 400 nm to 800 nm increased by up to ≈ 3%, while the sheet resistance Rsh strongly decreased by up to ≈ 82% at all concentrations. We correlated the changes with morphological changes visible in scanning and transmission electron microscopy and identified two sequential ageing stages: (I) post-plasma relaxation effects in and consolidation of the shell, and (II) particle re-organization, de-mixing, coarsening, and densification of the core with plating of Au from the core onto the shell, followed by solid-state de-wetting (ink concentrations cAu < 15 mg mL−1) or stability (cAu ≥ 15 mg mL−1). The plating of Au from the hybrid core improved the FTEs' Figure of Merit FOM = [T with combining macron]400–800·Rsh−1 by up to ≈ 5.8 times and explains the stable value of ≈ 3.3%·Ωsq−1 reached after 7 days of ageing at cAu = 30 mg mL−1.

Lactobacilli are gram-positive bacteria that are growing in importance for the healthcare industry and genetically engineering them as living therapeutics is highly sought after. However, progress in this field is hindered since most strains are difficult to genetically manipulate, partly due to their complex and thick cell walls limiting our capability to transform them with exogenous DNA. To overcome this, large amounts of DNA (>1 µg) are normally required to successfully transform these bacteria. An intermediate host, like E. coli, is often used to amplify recombinant DNA to such amounts although this approach poses unwanted drawbacks such as an increase in plasmid size, different methylation patterns and the limitation of introducing only genes compatible with the intermediate host. In this work, we have developed a direct cloning method based on in-vitro assembly and PCR amplification to yield recombinant DNA in significant quantities for successful transformation in L. plantarum WCFS1. The advantage of this method is demonstrated in terms of shorter experimental duration and the possibility to introduce a gene incompatible with E. coli into L. plantarum WCFS1.