62 research outputs found
Design von linearen und verzweigten Blockcopolymerarchitekturen mittels anionischer Polymerisation zur Untersuchung des Einflusses auf die Mikrophasenseparation
No full textIm Rahmen dieser Arbeit soll die Selbstanordnung komplexer Blockcopolymer-Architekturen sowie die Beeinflussung der Selbstanordnung von linearen Blockcopolymeren durch Additive untersucht werden. Dabei dient die anionische Polymerisation als Werkzeug zur Generierung der verschiedenen Blockcopolymere. Diese Methode ermöglicht ein hohes Maß an Kontrolle bei der Umsetzung von Monomeren hin zu einheitlichen Polymerstrukturen und somit zur Aufklärung von polymeren Struktur-Eigenschaftsbeziehungen. Die synthetisierten Polymere werden hinsichtlich ihrer Zusammensetzung und Größe charakterisiert. Die Mikrophasenseparation der entstandenen Blockcopolymere wird über Mikroskopie und Streumethoden analysiert. Auf Basis der erhaltenen Ergebnisse kann der Prozess der Selbstanordnung untersucht werden. Es kann über das gezielte Design der Mikrostruktur der Blockcopolymere auf eine Krümmung der Grenzfläche für sich ausbildende Morphologien im Zuge der Mikrophasenseparation Einfluss genommen werden. Das so generierte Wissen kann zukünftig den Weg zu neuen Produkten und Anwendungen ebnen. Zu den möglichen kommerziellen Produkten, die auf mikrophasenseparierten Copolymeren beruhen, zählen z.B. die thermoplastischen Elastomere. Neben der stetigen Verbesserung der Produkteigenschaften ist die Umstellung auf Monomere aus nachwachsenden Rohstoffen für die angestrebte Kreislaufwirtschaft essentiell. Somit werden die aufgefundenen Strategien und Syntheserouten auch auf biobasierte Monomere adaptiert.The scope of this thesis is the analysis of the self-assembly behavior of complex block copolymer architectures, as well as the influence of additives on the self-assembly of linear block copolymers. The used anionic polymerization is a versatile tool to generate different block copolymers. This method allows the synthesis of uniform polymer structures by enabling a high reaction control and is thereby useful in investigating the structure-property-relationship. The thereby synthesized polymers are characterized each by size and composition. Microphase separation is analyzed by microscopy and scattering methods. These results lead to a deeper understanding of the process of self-assembly. It is possible to gain insights in the role of linking points of different polymer architectures on the curvature of the inter material dividing surface of the resulting morphologies and their influence on microphase separation. This fundamental research is helpful to pave the way to new products and applications. Possible commercial products, which rely on the microphase separation of copolymers are i. e. thermoplastic elastomers. Additional to the optimization of existing products a change to monomers from renewable resources is necessary to get to circular economy. The strategies and synthesis can be adapted towards bio-based monomers
Ultrahigh-vacuum, high pressure and temperature infrared-ultraviolet-visible spectrophotometer cell
No full textAmphiphilic water soluble cationic ring opening metathesis copolymer as an antibacterial agent
No full textBacterial infection is a global problem, especially resistance acquired by bacteria against to antibiotics; there is urgent need for the development of antibiotics. Here, we proposed dendron-grafted polymers via ring opening metathesis polymerization (ROMP) featuring different with tailored hydrophobicity/hydrophilicity and cationic charges. Dendritic oxanorbornene derivatives were synthesized having two and six carbon linkers and their corresponding random and block copolymers were prepared having pendant pyridinium salt moieties via ROMP. In total, 12 different water-soluble dendronized cationic polymers featuring hexyl pyridinium moieties were prepared and investigated. Six carbon linker possessing triple charge density and hexyl pyridinium functionality each repeating unit copolymers exhibited high antibacterial activity against Gram-positive bacteria (S. aureus). However, all the polymers were inactive against Gram-negative bacteria (E. coli). Most of the copolymers are non-hemolytic (>HC (50) = 1,000 mu g/ml). It was also observed that, there is no significant effect between block copolymers and random copolymers keeping hydrophobicity and cationic charge density constant. Zeta potential was measured to investigate the mechanism in solution via the interaction of polymers with S. aureus, while scanning electron microscope (SEM) measurements image confirms damage of the bacterial cell wall after implementation of biocidal polymer
METHANOL AND ETHANOL OXIDATIVE DEHYDROGENATION (ODH) TO THE CORRESPONDING ALDEHYDES ON VANADIUM-BASED CATALYSTS
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Quenching of material dependence in few-cycle driven electron acceleration from nanoparticles under many-particle charge interaction
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Design of Aromatic Ring-Based Polyphosphonium Salts Synthesized via ROMP and the Investigation into Their Antibacterial and Hemolytic Activities
No full textIn this study, phosphonium salt-bearing polynorbornenes were synthesized using five different aromatic side chains (triphenylphosphonium, trifluorophenyl phosphonium, trichlorophenyl phosphonium, tri(p-tolyl)phosphonium, and cyclohexyldiphenyl phosphonium) via ring-opening metathesis polymerization (ROMP). The biological activities of these polymers were determined by their minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Escherichia coli and Staphylococcus aureus, and additionally, cytotoxicity studies on red blood cells were performed to report on their hemolytic activities (HC50). All of the synthesized polymers were found to be more active toward S. aureus than E. coli, and among them, tri(p-tolyl)phosphonium- and cyclohexyldiphenyl phosphonium-bearing homopolymers were found to be the most active against S. aureus (MIC: 2 μg mL-1) under the Mueller Hinton Broth (MHB) medium; however, the polymers were also found to be hemolytic (HC50 ≤ 8 μg mL-1). The electron densities of the monomers were calculated via computational studies to investigate the structure-property relationship for the biocidal activities of polymers. Furthermore, the morphological changes of the bacteria in the presence of the polymers were investigated by scanning electron microscopy (SEM) and zeta potential studies using dynamic light scattering (DLS) to speculate about the killing mechanism of the biocidal polymers. In the second part of this study, a series of copolymers were also synthesized to obtain selective copolymers, i.e., nontoxic and biocidal polymers. Using proper monomer compositions in copolymer series, the selectivity against S. aureus versus human red blood cells was determined to be 128.
Molecular ring rotation in poly(vinylferrocene)
No full textWe investigate the ring rotation dynamics in poly(vinylferrocene) (PVFc) using incoherent neutron spectroscopy. PVFc contains ferrocene units laterally attached to a polymer backbone, allowing for one cyclopentadienyl ring of the organometallic sandwich structure of ferrocene to undergo rotational jump diffusion. The barrier of rotation is found to be broadly distributed, but the dynamics can be well described using a rotation rate distribution model which is well known from the description of methyl group rotation in glassy polymers. As necessary information for the analysis of quasielastic scattering data, we measure the static structure factor of the polymer using polarized neutron diffraction. Neutron time-of-flight and backscattering data are then combined and consistently modeled over the large temperature range from 80 K to 350 K yielding an Arrhenius behavior of the jump rate distribution. The mean value of potential barrier distribution is found to be = 9.61(2) kJ mol(-1) with a root mean square width of sigma(E) = 3.12(1) kJ mol(-1), being the result of superposition of constant intramolecular and heterogeneous intermolecular rotational barriers
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