Synthesis of Sequence-Controlled Copolymers via Ring-Opening Metathesis Polymerization of Norbornene Derivatives

Seit dem Aufkommen der Polymerchemie, zu Beginn des zwanzigsten Jahrhunderts, steigt die Nachfrage nach funktionalisierten Polymeren kontinuierlich an. Des Weiteren werden hoch spezialisierte Polymere zukünftig vermutlich weiter an Bedeutung gewinnen. Die Natur dient in vielen Forschungsbereichen als Vorbild, so auch in der Polymerchemie. Die Kontrolle über die Monomersequenz in synthetischen Materialien, inspiriert von der definierten Abfolge von Nukleinbasen in der Desoxyribonukleinsäure (DNA), ermöglicht die Beeinflussung von intramolekularen Wechselwirkungen und damit der polymeren Mikrostruktur. Diese Struktur hat weiterhin einen Einfluss auf potenziell interessante makroskopische Eigenschaften des Polymers. Die Entwicklung von kontrollierten Polymerisationstechniken hat eine stabile Grundlage geschaffen, um sequenzkontrollierte Makromoleküle zu synthetisieren und entsprechende Forschungsziele zu erreichen. Als solche stellt die Ringöffnungsmetathese Polymerisation (ROMP) eine vielseitige Plattform dar, um funktionalisierte und sequenzkontrollierte Polymere zu synthetisieren. Im ersten Abschnitt dieser Dissertation wird eine Vielzahl an funktionalisierten Polymeren synthetisiert, wobei sich die verwendete Methode durch ihre Robustheit und Vielseitigkeit auszeichnet. Dabei werden Norbornen-funktionalisierte Carbonsäurederivate mit unterschiedlichen Aldehyden und Isocyaniden in einer Passerini-Dreikomponentenreaktion (P-3KR) umgesetzt. Die resultierenden bifunktionellen Monomere werden anschließend in einer ROMP zu den entsprechenden Polymeren umgesetzt. Des Weiteren wird der Einfluss der Monomerstruktur auf deren Polymerisierbarkeit und die Polymerisationskinetik untersucht. Die thermischen Eigenschaften der synthetisierten Polymere werden anschließend mit Hilfe dynamischer Differenzkalorimetrie (DDK) und thermogravimetrischer Analyse (TGA) ermittelt. Im zweiten Abschnitt der Dissertation werden verschiedene ROMP-basierte Synthesemethoden untersucht, um Pfropfcopolymere zu erzeugen. Hierfür werden zunächst Norbornen-funktionalisierte Makromonomere durch radikalische Polymerisation unter Atomtransfer (ATRP) synthetisiert und anschließend deren Homo- und Copolymerisierbarkeit mittels ROMP untersucht. Der Einfluss der Makromonomerstruktur auf die Polymerisationskinetik und die Polymerisationskontrolle wird mit Hilfe grundlegender Analysemethoden erforscht. Außerdem wird die iterative Synthese von sequenzkontrollierten Pfropfcopolymeren durch die Copolymerisation von unterschiedlichen Makromonomeren mittels ROMP untersucht und diskutiert. Zuletzt wird eine neue Strategie zur Synthese von bifunktionellen Makromonomeren mittels P-3KR vorgestellt, die einen einfachen Zugang zu ROMP-basierten Pfropfcopolymeren bietet. Im dritten Abschnitt dieser Dissertation wird die Synthese von sequenzkontrollierten Pfropfcopolymeren erforscht, wobei Norbornen-funktionalisierte Makromonomere nacheinander zu einer kontinuierlich fortschreitenden ROMP gegeben werden. Die verzögerte Zugabe von exoNorbornen-funktionellen Makromonomeren, die hohe Polymerisationsgeschwindigkeiten aufweisen, zu der relativ langsamen Polymerisation eines endo Norbornenderivates führt zu dem gezielten Einbau eines makromolekularen Blocks in das polymere Rückgrat. Hierbei wird der Einfluss der Makromonomerstruktur auf die Polymerisationskinetik und die Polymerisationskontrolle erforscht. Mit Hilfe dieses kinetischen Ansatzes können sequenzkontrollierte Pfropfcopolymere synthetisiert werden. Die Verwendung von verschiedenen Makromonomeren führt zu diblock-, sowie triblockartigen Architekturen und ermöglicht die Variation der entsprechenden Molfraktionen auf kontrollierte Weise. Insgesamt wurden die angewendeten Methoden erfolgreich durchgeführt, obgleich der vielfach berichtete sequenzielle Einbau von (Makro)monomeren in ein „lebendes“ Polymer als die ineffizienteste und am stärksten limitierte Methode identifiziert wurde. Ein weitaus vielversprechenderer Ansatz wurde mit Hilfe eines (in diesem Bereich) größtenteils übersehenen Katalysators erarbeitet. Dieser Ansatz nutzt die speziellen kinetischen Eigenschaften von Norbornen-Isomeren aus und stellt ein vielseitiges Verfahren zur Synthese von sequenzkontrollierten Pfropfcopolymeren dar. Außerdem wurden Multikomponentenreaktionen erfolgreich zur Synthese von bifunktionellen Monomeren verwendet, die anschließend in sequenzkontrollierte Polymere umgewandelt wurden

Ring‐Opening Metathesis Polymerization of Norbornene‐Based Monomers Obtained via the Passerini Three Component Reaction

Ring-opening metathesis polymerization is a robust method to synthesize a variety of polymers by using ring-strained molecules as monomers, e.g., norbornenes. However, the synthesis of monomers with multiple functional groups remains a challenge, albeit peptide functional norbornenes have previously been used. Here, the Passerini three component reaction is exploited to synthesize norbornenes with two variable functional groups varying in bulkiness and distance from the polymerizable alkene. The results indicate that the functional groups do not affect the kinetics of the polymerization, whereas the length of the linker has a minor effect. Furthermore, a diblock-type copolymer is synthesized in a one-pot fashion, also indicating good control of the polymerization process. The thermal properties of all polymers are evaluated, highlighting the effect of monomer composition. This synthetic approach can be transferred to a variety of compounds, thus promising highly diverse polymers with complex compositions and architectures

One‐Pot Synthesis of Thiocarbamates

An efficient isocyanide-based synthesis of S-thiocarbamates was discovered and thoroughly investigated. The new reaction protocol is a one-pot procedure and allows the direct conversion of N-formamides into thiocarbamates by initial dehydration with p-toluene sulfonyl chloride to the respective isocyanide and subsequent addition of a sulfoxide component. Contrary to recent literature, which also uses isocyanides as starting material, but with other sulfur reagents than sulfoxides, in this protocol, no isolation and purification of the isocyanide component is necessary, thus significantly decreasing the environmental impact and increasing the efficiency of the synthesis. The new protocol was applied to synthesize a library of sixteen thiocarbamates, applying four N-formamides and four commercially available sulfoxides. Furthermore, experiments were conducted to investigate the reaction mechanism. Finally, four norbornene-based thiocarbamate monomers were prepared and applied in controlled ring-opening metathesis polymerization (ROMP) reactions. The polymers were characterized by size-exclusion chromatography (SEC) and their properties were investigated utilizing differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)

Model Predictive Control with Binary Quadratic Programming for the Scheduled Operation of Domestic Refrigerators

The rapid proliferation of the ‘Internet of Things’ (IoT) now affords the opportunity to schedule the operation of widely distributed domestic refrigerator and freezers to collectively improve energy efficiency and reduce peak power consumption on the electrical grid. To accomplish this, the paper proposes the real-time estimation of the thermal mass of each refrigerator in a network using on-line parameter identification, and the co-ordinated (ON-OFF) scheduling of the refrigerator compressors to maintain their respective temperatures within specified hysteresis bands commensurate with accommodating food safety standards. A custom model predictive control (MPC) scheme is devised using binary quadratic programming to realize the scheduling methodology which is implemented through IoT hardware (based on a NodeMCU). Benefits afforded by the proposed scheme are investigated through experimental trials which show that the co-ordinated operation of domestic refrigerators can i) reduce the peak power consumption as seen from the perspective of the electrical power grid (i.e., peak load levelling), ii) can adaptively control the temperature hysteresis band of individual refrigerators to increase operational efficiency, and iii) contribute to a widely distributed aggregated load shed for demand side response purposes in order to aid grid stability. Importantly, the number of compressor starts per hour for each refrigerator is also bounded as an inherent design feature of the algorithm so as not to operationally overstress the compressors and reduce their lifetime. Experimental trials show that such co-ordinated operation of refrigerators can reduce energy consumption by ~30% whilst also providing peak load levelling, thereby affording benefits to both individual consumers as well as electrical network suppliers

Biocompatible unimolecular micelles obtained via the Passerini reaction as versatile nanocarriers for potential medical applications

A Passerini three-component polymerization was performed for the synthesis of amphiphilic star-shaped block copolymers with hydrophobic cores and hydrophilic coronae. The degree of polymerization of the hydrophobic core was varied from 5 to 10 repeating units, and the side chain ends were conjugated by performing a Passerini-3CR with PEG-isocyanide and PEG-aldehyde (950 g/mol). The resulting amphiphilic star-shaped block copolymers contained thioether groups, which could be oxidized to sulfones in order to further tune the polarity of the polymer chains. The ability of the amphiphilic copolymers to act as unimolecular micellar encapsulants was tested with the water-insoluble dye Orange II, the water-soluble dye Para Red and the macrolide antibiotic azithromycin. The results showed that the new copolymers were able to retain drug cargo at pH levels corresponding to circulating blood and selectively release therapeutically effective doses of antibiotic as measured by bacterial cell kill. The polymers were also well-tolerated by differentiated THP-1 macrophages in the absence of encapsulated drugs

Membedah mitos-mitos budaya massa : semiotika atau sosiologi tanda, simbol, dan representasi/ Barther

lxxii, 364 hal.; 21 cm

Occupancy Grid Mapping with Highly Uncertain Range Sensors based on Inverse Particle Filters

Korthals T, Barther M, Schöpping T, Herbrechtsmeier S, Rückert U. Occupancy Grid Mapping with Highly Uncertain Range Sensors based on Inverse Particle Filters. In: Proceedings of the 13th International Conference on Informatics in Control, Automation and Robotics. 2016: 192-200.A huge number of techniques for detecting and mapping obstacles based on LIDAR and SONAR exist, though not taking approximative sensors with high levels of uncertainty into consideration. The proposed mapping method in this article is undertaken by detecting surfaces and approximating objects by distance using sensors with high localization ambiguity. Detection is based on an Inverse Particle Filter, which uses readings from single or multiple sensors as well as a robot’s motion. This contribution describes the extension of the Sequential Importance Resampling filter to detect objects based on an analytical sensor model and embedding into Occupancy Grid Maps. The approach has been applied to the autonomous mini robot AMiRo in a distributed way. There were promising results for its low-power, low-cost proximity sensors in various real life mapping scenarios, which outperform the standard Inverse Sensor Model approach

Heart rate influence on the QT variability risk factors

QT interval variability, mostly expressed by QT variability index (QTVi), has repeatedly been used in risk diagnostics. Physiologic correlates of QT variability expressions have been little researched especially when measured in short 10-second electrocardiograms (ECGs). This study investigated different QT variability indices, including QTVi and the standard deviation of QT interval durations (SDQT) in 657,287 10-second ECGs recorded in 523 healthy subjects (259 females). The indices were related to the underlying heart rate and to the 10-second standard deviation of RR intervals (SDRR). The analyses showed that both QTVi and SDQT (as well as other QT variability indices) were highly statistically significantly (p < 0.00001) influenced by heart rate and that QTVi showed poor intra-subject reproducibility (coefficient of variance approaching 200%). Furthermore, sequential analysis of regression variance showed that SDQT was more strongly related to the underlying heart rate than to SDRR, and that QTVi was influenced by the underlying heart rate and SDRR more strongly than by SDQT (p < 0.00001 for these comparisons of regression dependency). The study concludes that instead of QTVi, simpler expressions of QT interval variability, such as SDQT, appear preferable for future applications especially if multivariable combination with the underlying heart rate is used