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Organisationseinheit der BAM
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Materials that respond to the environment by changing their properties are critical for developing
autonomously adaptive systems. However, to reversibly influence a material's inherent characteristics, such as its ability to self-heal, from distance without continuously expending energy, remains a challenging task. Herein, we report on the modul at ion of imine exchange kinetics by light, manifested in a remote controllable dynamic covalent polymer network. Simple mixing of a commercially available amino-functionalized polysiloxane with small amounts of a photoswitchable diarylethene cross-linker, carrying two aldehyde groups, yields a rubbery material. Its viscoelastic and self-healing properties can be reversibly tuned with everyday light sources, such as sunlight. Our two-component system offers the unique advantage that self-healing takes place continuously without any additives at ambient conditions and is neither dependent on continuous illumination nor does it require recent damage. Overall, our approach allows for the local amplification of intrinsic material properties in a permanent yet reversible fashion. The availability of the inexpensive sta1ting materials on a multi-gram scale, the easy synthesis of the polymer network, and its convenient handling paired with high versatility make our Approach highly applicable to create custom-tailored adaptive materials.
Healable materials are able to repair inflicted damages, herin often applied: dynamic covalent polymer networks. We have shown in this study that light of different colors shift the Diels-Alder and retro Diels-Alder crosslinking and decrosslinking equilibrium. This effect was utilized for self-healing of a polymer film. Small-angle X-ray scattering was used to quantifiy the polymeric mesh size on a nanoscale.
Phage display is used to find specific target binding peptides for polypropylene (PP) surfaces. PP is one of the most commonly used plastics in the world. Millions of tons are produced every year. PP binders are of particular interest because so far gluing or printing on PP is challenging due to its low surface energy. A phage display protocol for PP was developed followed by Next Generation DNA Sequencing of the whole phage library. Data analysis of millions of sequences yields promising peptide candidates which were synthesized as PEG conjugates. Fluorescence-based adsorption-elution-experiments show high adsorption on PP for several sequences.
Finally, it can be summarized that the second edition of this popular textbook provides a comprehensive overview on the practical basics and applications of conducting polymers. It fulfills its intension of assisting various researchers from diverse fields to become familiar with fundamentals and applications of conducting polymers.
Fiber-reinforced-polymers (FRPs) are in current research focus in the lightweight construction industry, because of their extraordinary characteristics (stiffness and strength-to-density relation). The structure of polymer matrix and the interaction with reinforcement are crucial for optimization of the mechanical and thermal properties of FRPs. Due to the macromolecular chain structure, the mechanical properties of a polymer strongly vary with temperature: Below the glass transition, the chain segments of a polymer are “frozen”. Regarding fracture, the total changed energy during fracture if only dissipates for the generation of the new surfaces. However, in the region of the glass transition, the polymer chain segments start to get “unfrozen”, and the energy is not only required for generating new surfaces, but also for irreversibly deformation. This irreversible deformation is affected by the global temperature and the local temperature near the crack tip, which is affected by the local strain rate and crack propagation velocity.
Hence, in this research project, the irreversible deformation of neat and reinforced polymers will be controlled by changing the global temperature as well as the local temperature. With using different fracture experiments, the amount of energy required for creating new surfaces and for the irreversible deformation will be separated. The fracture tests include the conventional tensile test, the macroscopic peel test and the single fiber peel – off test.
Modern and energy-efficient materials are essential for innovative designs for aerospace and automotive industries. Current technologies for rapid manufacturing such as additive manufacturing and liquid composite moulding by polymer Extrusion allow innovative ways of creating robust and lightweight constructions. Commercially available printing devices often use polylactide (PLA) or acrylonitrile butadiene styrene (ABS) as raw material. Therefore, parameters like the infill ratio, influencing the ability to resist mechanical stress, may have a beneficial impact on the lifetime of components.
These manufacturing technologies require a good knowledge about materials and even adapted non-destructive testing technologies and methods. Airborne ultrasonic testing has beneficial advantages for testing those lightweight constructions. It is a contact-free testing method, which does not require a liquid couplant. Therefore, it allows fast test cycles without any unwanted alternations of the material properties due to interactions with any coupling liquid. This contribution deals with the characterisation of printed specimens based on PLA by using airborne ultrasound and presents the current edge of non-destructive testing and evaluation using airborne ultrasonic transducers. The specimens, manufactured by polymer extrusion, are printed as thin plates. The infill ratio, as well as the material thickness, were varied to model density imperfections with different geometric shapes and properties. For better understanding of the limits of airborne ultrasonic testing in transmission, we compared own-developed transducers based on different physical principles: on ferroelectrets, on the thermoacoustic effect, as well as a new type of transducers based on gas discharges.
Nach einer Übersicht zu den immer schneller aktualisierenden Rahmenbedingungen von Politik und Gesellschaft folgt eine Übersicht zu materialwissenschaftlichen Problemen des Recyclings von Kunststoffen. Lösungsansätze aus der Forschung reichen von einfacher Optimierung bis hin zur radikalen Neukonstruktion der polymeren Werkstoffe. Aus dem bereits möglichen Ansatz "performance-by-design" wird ein neuer Weg des "recycling-by-design" adressiert. Dies inkludiert methodisch eine skalenübergreifende Modellierung und die Depolarisation bis zum Monomer.
Fiber-reinforced-polymers (FRPs) are in current research focus in the lightweight construction industry, because of their extraordinary characteristics (stiffness and strength-to-density relation). The structure of polymer matrix and the interaction with reinforcement are crucial for optimization of the mechanical and thermal properties of FRPs. Due to the macromolecular chain structure, the mechanical properties of a polymer strongly vary with temperature: Below the glass transition, the chain segments of a polymer are “frozen”. Regarding fracture, the total changed energy during fracture if only dissipates for the generation of the new surfaces. However, in the region of the glass transition, the polymer chain segments start to get “unfrozen”, and the energy is not only required for generating new surfaces, but also for irreversibly deformation. This irreversible deformation is affected by the global temperature and the local temperature near the crack tip, which is affected by the local strain rate and crack propagation velocity.
Hence, in this research project, the irreversible deformation of neat and reinforced polymers will be controlled by changing the global temperature as well as the local temperature. With using different fracture experiments, the amount of energy required for creating new surfaces and for the irreversible deformation will be separated. In this presentation, I summarized of the first 15 months the whole project. In this period, the basic crack propagation theory for neat polymers is established and the special fracture experiment sample is prepared and tested at room temperature. In addition, the model of the specimen is first established.
In this also completely rewritten and reorganized second part of the two‐volume set 45 international experts comprise the current knowledge of conjugated polymers. In addition to part one on properties, processing characterization and morphology, 16 chapters cover perspectives, theory and new materials.
Finally, it can be concluded that this 4th edition of this handbook fulfills, like the first part, its intention, to be the definitive resource on the topic of conducting polymers. This is assured by the updated and added contributions of all authors, which consider the significant developments both in fundamental understanding, progress and applications since publication of the previous edition. So, it can be recommended to everyone, who wants to get a comprehensive overview on conjugated polymers, not just to researchers, advanced students, and industry professionals working in materials science and engineering.