Compression-Responsive Photonic Crystals Based on Fluorine-Containing Polymers

Fluoropolymers represent a unique class of functional polymers due to their various interesting and important properties such as thermal stability, resistance toward chemicals, repellent behaviors, and their low refractive indices in comparison to other polymeric materials. Based on the latter optical property, fluoropolymers are particularly of interest for the preparation of photonic crystals for optical sensing application. Within the present study, photonic crystals were prepared based on core-interlayer-shell particles focusing on fluoropolymers. For particle assembly, the melt-shear organization technique was applied. The high order and refractive index contrast of the individual components of the colloidal crystal structure lead to remarkable reflection colors according to Bragg’s law of diffraction. Due to the special architecture of the particles, consisting of a soft core, a comparably hard interlayer, and again a soft shell, the resulting opal films were capable of changing their shape and domain sizes upon applied pressure, which was accompanied with a (reversible) change of the observed reflection colors as well. By the incorporation of adjustable amounts of UV cross-linking agents into the opal film and subsequent treatment with different UV irradiation times, stable and pressure-sensitive opal films were obtained. It is shown that the present strategy led to (i) pressure-sensitive opal films featuring reversibly switchable reflection colors and (ii) that opal films can be prepared, for which the written pattern—resulting from the compressed particles—could be fixed upon subsequent irradiation with UV light. The herein described novel fluoropolymer-containing photonic crystals, with their pressure-tunable reflection color, are promising candidates in the field of sensing devices and as potential candidates for anti-counterfeiting materials

Complex 3D‐Printed Mechanochromic Materials with Iridescent Structural Colors Based on Core–Shell Particles

A scalable protocol for design and subsequent 3D-printing of polymeric coreshell-particles is reported. The particle synthesis by emulsion polymerization in starved-feed mode is used for tailoring particle architecture and composition. Control of size, mechanical properties, and chemical functionalities allow to achieve the specific requirement profile for subsequent extrusion-based additive manufacturing. The core-shell particles consist of hard polystyrene cores and a comparably soft polyalkylacrylate-based shell. Size and monodispersity, as well as core-to-shell ratio, are determined by means of dynamic light scattering and transmission electron microscopy. Thermal and rheological properties are investigated by means of dynamic scanning calorimetry and thermogravimetric analysis as well as oscillation and capillary rheometry. During 3D-printing, the monodisperse particles self-assemble into an ordered close packed lattice structure, leading to visible reflection colors according to Bragg’s law of diffraction. Distinct and angle-dependent reflection colors are recorded via UV-vis spectroscopy. As the structural color depends, inter alia, on the underlying particle sizes, resulting colors are easily tunable by adjusting the applied synthesis parameters. Under mechanical deformation, the color changes due to controlled lattice deformation, which enables mechanochromic sensing with the printed objects. They are also promising candidates for decorative ornaments, smart optical coatings, or advanced security devices

Etablierung und Charakterisierung eines in vivo RNA-Rekombinationssystems : Mechanistische Studien und Erzeugung rekombinanter Pestiviren

Im Rahmen dieser Arbeit konnte das erste Zellkultursystem für die pestivirale RNA-Rekombination etabliert werden. Es stellt im Vergleich zur alleinigen Sequenzanalyse natürlich entstandener rekombinanter Pestivirusgenome einen erheblichen Fortschritt dar. Das System erlaubt nach Transfektion eines nicht replikationskompetenten Transkripts in mit nichtzytopathogenem (nzp) Virus infizierte Zellen und auch nach Kotransfektion von zwei synthetischen RNAs in nicht infizierte Zellen die effiziente Generierung rekombinanter Pestiviren. Dieser Versuchsansatz ahmt in Zellkultur die Entstehung von zytopathogenen (zp) Genomen des Virus der bovinen viralen Diarrhöe (BVDV) im Tier nach. Er erlaubte es, bereits zuvor aufgestellte Arbeitshypothesen wie die Abhängigkeit der RNA-Rekombinationsfrequenz von der zur Verfügung stehenden Menge eines Rekombinationspartners zu bestätigen. Ausserdem zeigte die Analyse von 46 „crossover“-Regionen, die jeweils durch Rekombination zwischen demselben Paar von parentalen RNAs entstanden waren, eine mögliche Beteiligung von Basenpaarung an einem hypothetischen, replikativen Rekombinationsprozess. Dabei konnte unter anderem das bislang größte pestivirale Genom identifiziert werden, dessen Länge die eines nzp Virus um fast 60 % übertrifft. Weitere Untersuchungen zum Mechanismus der RNA-Rekombination deuteten darauf hin, dass zumindest in diesem System RNA-Rekombination hauptsächlich in den ersten Stunden nach der Transfektion synthetischer RNAs stattfand. Desweiteren scheint replikative RNA-Rekombination von Pestiviren nicht (oder nur sehr eingeschränkt) während der viralen Plusstrangsynthese stattzufinden. Es konnte auch gezeigt werden, dass der pestivirale Replikationskomplex die Plusstrangsynthese am 3´-Ende eines (synthetischen) Minusstrangs in trans nicht initiieren kann. Die Möglichkeit zur gezielten Beeinflussung beider Rekombinationspartner erlaubte Studien, welche die Unabhängigkeit der RNA-Rekombination von der autonomen Replikationskompetenz beider Rekombinationspartner beweisen. Dabei konnten einzigartige rekombinante nzp BVD-Viren isoliert werden. Über die Bestimmung der Herkunft der 3´NTR rekombinanter viraler Genome wurde für das Rekombinationssystem ein doppelter \u27template switch\u27 zwischen den eingesetzten Rekombinationspartnern während der viralen Minusstrangsynthese ausgeschlossen. Als wichtigstes Ergebnis belegen im Rahmen dieser Arbeit durchgeführte Versuche, dass in der Zelle ein bislang nicht näher charakterisierter Mechanismus für die Rekombination von RNAs existiert, der von der Anwesenheit einer viralen RNA-abhängigen RNA-Polymerase (RdRp) unabhängig ist. Eine End- zu Endligation der beteiligten Rekombinationspartner scheint dabei keine Rolle zu spielen. Die weitreichende Bedeutung dieses Phänomens für die Evolution und Zellbiologie ist noch nicht abzusehen. Das Rekombinationssystem wurde zur Klärung der Frage eingesetzt, ob die Entstehung eines von einem Helfervirus unabhängigen zp Genoms des Virus der klassischen Schweinepest (KSPV) durch RNA-Rekombination möglich ist. Ein solches KSPV war bislang weder aus infizierten Tieren noch aus Zellkulturpassagen eines nzp Virus isoliert worden. Durch erfolgreiche Adaptation des Rekombinationssystems an KSPV konnte das von einem Helfervirus unabhängige zp KSPV (CP G1) erzeugt werden. Exemplarisch wurde für CP G1 gezeigt, dass Helfervirus-unabhängige zp Stämme für eine vereinfachte Durchführung von Serumneutralisationstests in der KSPV-Diagnostik geeignet erscheinen. Zusammengefasst zeigt diese praktische Anwendung, dass das vorliegende Rekombinationssystem als Alternative zum klassischen Mutationsweg über reverse Genetik ein flexibel einsetzbares Wekzeug darstellt. Dieses System kann u.a. zur Generierung rekombinanter (Pesti)-Viren von erwünschtem Phänotyp (z.B. von zp Genomen) sowie zur gezielten Mutation definierter Bereiche eines viralen Genoms (z.B. von RdRp-Mutanten) eingesetzt werden.In this study the first cell culture system for RNA recombination of pestiviruses was established. It represents a considerable progress when compared to sequence analyses of naturally emerged recombinant pestiviral isolates only. This system allowed the efficient generation and subsequent characterization of recombinant pestiviral genomes after transfection of a synthetic and replication incompetent RNA into cells infected with a noncytopathogenic (noncp) virus. In addition, recombination was also observed when two synthetic transcripts were transfected into noninfected cells. This cell culture system mimics the emergence of cytopathogenic (cp) Bovine viral diarrhea virus (BVDV) genomes within the infected animal and dependably allowed to prove hypotheses concerning RNA recombination. These findings included the correlation of RNA recombination frequency with the amount of one recombination partner. Moreover, analyses of fourtysix crossover sites each originating from recombination between the same pair of parental RNAs suggested that basepairing might have facilitated replicative template switching. Upon these analyses, the largest pestiviral genome ever described was identified which genome length exceeds that of a noncp pestivirus by almost sixty percent. Subsequent investigations concerning the mechanism of RNA recombination suggest that, at least in this system, recombination seems to take place mainly within the first hours after the transfection of synthetic RNAs. Moreover, replicative RNA recombination of pestiviruses seems not to (or only restrictedly) occur during viral plus strand synthesis. These studies also revealed that the pestiviral replication complex is not able to initiate synthesis of plus strands at a (synthetic) pestiviral minus strand in trans. Being given the possibility to selectively manipulate both recombination partners, additional experiments were performed that demonstrated the occurrence of RNA recombination between two replication incompetent transcripts. Thereby, unique recombinant noncp BVDV genomes could be isolated. Furthermore, by determining the origin of the viral 3´NTR of emerged recombinant genomes, for this system a double template switch during viral minus strand synthesis could be excluded. Most importantly, our studies showed that a unique, so far uncharacterized mechanism of RNA recombination exists in vivo that is independent from the presence of a functional viral RNA-dependent RNA-polymerase (RdRp). Here, an end to end ligation of RNA molecules that participate in recombination was obviously not involved. The relevance of this phenomenon for evolution and its impact on cell biology are yet to be determined. Finally, the recombination system was used to elucidate the question, whether - although never being isolated from infected animals or cell culture passages of a noncp virus - a helper virus independent cp Classical swine fever virus (CSFV) can be generated by RNA recombination. By successful adaptation of the recombination system to CSFV the unique helper virus independent cp CSFV strain CP G1 was generated. As it was exemplarily demonstrated for CP G1, helper virus independent cp strains could facilitate accomplishment of serum neutralization assays for diagnosis of Classical swine fever. Taken together, this practical application demonstrates that, as an alternative to classical reverse genetics, the established recombination system represents a powerful und versatile tool. It is appropriate not only for generation of recombinant (pesti)viruses exhibiting a desired phenotype (e.g., cp genomes), but also for targeted mutation of defined regions of a viral genome (e.g., RdRp-mutants)

Dye-Loaded Mechanochromic and pH-Responsive Elastomeric Opal Films

In this work, the preparation and fabrication of elastomeric opal films revealing reversible mechanochromic and pH-responsive features are reported. The core–interlayer–shell (CIS) particles are synthesized via stepwise emulsion polymerization leading to hard core (polystyrene), crosslinked interlayer (poly(methyl methacrylate-co-allyl methacrylate), and soft poly(ethyl acrylate-co-butyl acrylate-co-(2-hydroxyethyl) methacrylate) shell particles featuring a size of 294.9 ± 14.8 nm. This particle architecture enables the application of the melt-shear organization technique leading to elastomeric opal films with orange, respectively, green brilliant reflection colors dependent on the angle of view. Moreover, the hydroxyl moieties as part of the particle shell are advantageously used for subsequent thermally induced crosslinking reactions enabling the preparation of reversibly tunable mechanochromic structural colors based on Bragg's law of diffraction. Additionally, the CIS particles can be loaded upon extrusion or chemically by a postfunctionalization strategy with organic dyes implying pH-responsive features. This convenient protocol for preparing multi-responsive, reversibly stretch-tunable opal films is expected to enable a new material family for anti-counterfeiting applications based on external triggers

Dye-Loaded Mechanochromic and pH-Responsive Elastomeric Opal Films

In this work, the preparation and fabrication of elastomeric opal films revealing reversible mechanochromic and pH-responsive features are reported. The core-interlayer-shell (CIS) particles are synthesized via stepwise emulsion polymerization leading to hard core (polystyrene), crosslinked interlayer (poly(methyl methacrylate-co-allyl methacrylate), and soft poly(ethyl acrylate-co-butyl acrylate-co-(2-hydroxyethyl) methacrylate) shell particles featuring a size of 294.9 ± 14.8 nm. This particle architecture enables the application of the melt-shear organization technique leading to elastomeric opal films with orange, respectively, green brilliant reflection colors dependent on the angle of view. Moreover, the hydroxyl moieties as part of the particle shell are advantageously used for subsequent thermally induced crosslinking reactions enabling the preparation of reversibly tunable mechanochromic structural colors based on Bragg's law of diffraction. Additionally, the CIS particles can be loaded upon extrusion or chemically by a postfunctionalization strategy with organic dyes implying pH-responsive features. This convenient protocol for preparing multi-responsive, reversibly stretch-tunable opal films is expected to enable a new material family for anti-counterfeiting applications based on external triggers

Mechanically Stable, Binder‐Free, and Free‐Standing Vanadium Trioxide/Carbon Hybrid Fiber Electrodes for Lithium‐Ion Batteries

Binder is a crucial component in present-day battery electrodes but commonly contains fluorine and requires coating processing using organic (often toxic) solvents. Preparing binder-free electrodes is an attractive strategy to make battery electrode production and its end-of-use waste greener and safer. Herein, electrospinning is employed to prepare binder-free and self-standing electrodes. Such electrodes often suffer from low flexibility, and the correlation between performance and flexibility is usually overlooked. Processing parameters affect the mechanical properties of the electrodes, and for the first time it is reported that mechanical flexibility directly influences the electrochemical performance of the electrode. The importance is highlighted when processing parameters advantageous to powder materials, such as a higher heat treatment temperature, harm self-standing electrodes due to deterioration of fiber flexibility. Other strategies, such as conductive carbon addition, can be employed to improve the cell performance, but their effect on the mechanical properties of the electrodes must be considered. Rapid heat treatment achieves self-standing V2O3 with a capacity of 250 mAh g−1 at 250 mA g−1 and 390 mAh g−1 at 10 mA g−

Combining Soft Polysilazanes with Melt-Shear Organization of Core–Shell Particles: On the Road to Polymer-Templated Porous Ceramics

The preparation of ordered macroporous SiCN ceramics has attracted significant interest and is an attractive area for various applications, e.g., in the fields of catalysis, gas adsorption, or membranes. Non-oxidic ceramics, such as SiCN, own a great stability based on the covalent bonds between the containing elements, which leads to interesting properties concerning resistance and stability at high temperature. Their peculiar properties have become more and more important for a manifold of applications, like catalysis or separation processes, at high temperatures. Within this work, a feasible approach for the preparation of ordered porous materials by taking advantage of polymer-derived ceramics is presented. To gain access to free-standing films consisting of porous ceramic materials, the combination of monodisperse organic polymer-based colloids with diameters of 130 nm and 180 nm featuring a processable preceramic polymer is essential. For this purpose, the tailored design of hybrid organic/inorganic particles featuring anchoring sites for a preceramic polymer in the soft shell material is developed. Moreover, polymer-based core particles are used as sacrificial template for the generation of pores, while the preceramic shell polymer can be converted to the ceramic matrix after thermal treatment. Two different routes for the polymer particles, which can be obtained by emulsion polymerization, are followed for covalently linking the preceramic polysilazane Durazane1800 (Merck, Germany): (i) Free radical polymerization and (ii) atom transfer radical polymerization (ATRP) conditions. These hybrid hard core/soft shell particles can be processed via the so-called melt-shear organization for the one-step preparation of free-standing particle films. A major advantage of this technique is the absence of any solvent or dispersion medium, enabling the core particles to merge into ordered particle stacks based on the soft preceramic shell. Subsequent ceramization of the colloidal crystal films leads to core particle degradation and transformation into porous ceramics with ceramic yields of 18–54%

The core effector Cce1 is required for early infection of maize by Ustilago maydis

The biotrophic pathogen Ustilago maydis, the causative agent of corn smut disease, infects one of the most important crops worldwide – Zea mays. To successfully colonize its host, U. maydis secretes proteins, known as effectors, that suppress plant defense responses and facilitate the establishment of biotrophy. In this work, we describe the U. maydis effector protein Cce1. Cce1 is essential for virulence and is upregulated during infection. Through microscopic analysis and in vitro assays, we show that Cce1 is secreted from hyphae during filamentous growth of the fungus. Strikingly, Δcce1 mutants are blocked at early stages of infection and induce callose deposition as a plant defense response. Cce1 is highly conserved among smut fungi and the Ustilago bromivora ortholog complemented the virulence defect of the SG200Δcce1 deletion strain. These data indicate that Cce1 is a core effector with apoplastic localization that is essential for U. maydis to infect its host

Combining Soft Polysilazanes with Melt-Shear Organization of Core–Shell Particles: On the Road to Polymer-Templated Porous Ceramics

The preparation of ordered macroporous SiCN ceramics has attracted significant interest and is an attractive area for various applications, e.g., in the fields of catalysis, gas adsorption, or membranes. Non-oxidic ceramics, such as SiCN, own a great stability based on the covalent bonds between the containing elements, which leads to interesting properties concerning resistance and stability at high temperature. Their peculiar properties have become more and more important for a manifold of applications, like catalysis or separation processes, at high temperatures. Within this work, a feasible approach for the preparation of ordered porous materials by taking advantage of polymer-derived ceramics is presented. To gain access to free-standing films consisting of porous ceramic materials, the combination of monodisperse organic polymer-based colloids with diameters of 130 nm and 180 nm featuring a processable preceramic polymer is essential. For this purpose, the tailored design of hybrid organic/inorganic particles featuring anchoring sites for a preceramic polymer in the soft shell material is developed. Moreover, polymer-based core particles are used as sacrificial template for the generation of pores, while the preceramic shell polymer can be converted to the ceramic matrix after thermal treatment. Two different routes for the polymer particles, which can be obtained by emulsion polymerization, are followed for covalently linking the preceramic polysilazane Durazane1800 (Merck, Germany): (i) Free radical polymerization and (ii) atom transfer radical polymerization (ATRP) conditions. These hybrid hard core/soft shell particles can be processed via the so-called melt-shear organization for the one-step preparation of free-standing particle films. A major advantage of this technique is the absence of any solvent or dispersion medium, enabling the core particles to merge into ordered particle stacks based on the soft preceramic shell. Subsequent ceramization of the colloidal crystal films leads to core particle degradation and transformation into porous ceramics with ceramic yields of 18–54%