This paper reviews the synthesis and properties of nanostructural polymers with different macromolecular architecture. Special emphasis is placed on hyperbranched polymers, rod-like macromolecules ...and polymer brushes. Hyperbranched polymers were prepared by various types of living radical mechanisms of functionalized vinyl monomers and showed hard sphere-like behavior in dilute solution with increasing degree of branching. This reflected on the compact nature of the hyperbranched macromolecules. Rod-like macromolecules were prepared by crosslinking cylindrical microdomains of block copolymers in the solid state or cylindrical micelles in solution. In general, polymer brushes were prepared by homopolymerization or copolymerization of macromonomers. Both solutions of rod-like macromolecules and polymer brushes formed a unimolecule structure even in high concentration. Thus, the particular chemical structures of rod-like macromolecules and polymer brushes were influenced significantly by densely branched side chains.
The synthesis and characterization of terminal multiple hydrogen-bonded (MHB) polymers, such as poly(styrene) (PS), poly(isoprene) (PI), and microphase separated PS-b-PI block copolymers, possessing ...controlled molecular weights and narrow molecular distributions are described. Hydroxyl-terminated polymeric precursors were prepared using living anionic polymerization and subsequent quantitative termination with ethylene oxide. MHB polymers were synthesized in a controlled fashion via end-group modification of these well-defined macromolecular alcohols with excess isophorone diisocyanate and subsequent derivatization of the isocyanate-terminated polymeric intermediate with methyl isocytosine. The glass transition temperatures of the terminal MHB polymers were reproducibly higher than both nonfunctionalized and hydroxyl-terminated polymers at nearly equivalent number average molecular weights. Thin-layer chromatography analysis indicated that the interaction of terminal MHB polymers with silica was stronger as compared to both nonfunctionalized and hydroxyl-terminated polymers. Rheological characterization indicated that the melt viscosity at constant shear rate for various MHB polymers was more than 100 times higher than those for nonfunctionalized and hydroxyl-terminated polymers. Interestingly, the melt viscosity of MHB polymers was higher than those of nonfunctionalized polymers with twice the number average molecular weight. In addition, DSC and rheological characterization also suggested that terminal MHB polymers formed aggregates and not simple dimers in the melt state, and the aggregates were observed to completely dissociate at 80 °C.
Makromoleküle sind sehr große, aus einzelnen Bausteinen zu langen Ketten verknüpfte Moleküle. Die Architektur der entstehenden Gebilde ist vielfältig und bestimmt ganz wesentlich die Eigenschaften. ...Viele dieser Eigenschaften lassen sich mit bloßem Auge erkennen. Dies ist für das Experimentieren im Schülerlabor ideal, da ohne besondere Hilfsmittel ein Zusammenhang zwischen Struktur und Eigenschaften herstellbar ist. Das Projekt „Von Groß zu Klein“ im Agnes‐Pockels‐SchülerInnen‐Labor hatte das Ziel, Aufbau und Eigenschaften von Makromolekülen experimentell zu erschließen und anhand von Modellen zu erklären. Daraus werden beispielhaft Alginat als natürliches und Polyacrylat als synthetisches Polymer vorgestellt. An diesen beiden Polyelektrolyten lassen sich Gelierungsverhalten und Einflussgrößen darauf systematisch untersuchen. Auch anwendungsorientierte Experimente werden beschrieben. Die Versuche sind für die Sek. I konzipiert und können für Grundschule und Sek. II angepasst werden.
Translation
Macromolecules are built of small building blocks, covalently connected to long chains. There are a lot of architectures which materially determine their properties, many of which like viscosity or gelling are visible to the naked eye. This is of great benefit for children experimenting in a student‐lab, because it helps to understand structure‐property relationships. The project “from the big to the small” in the Agnes‐Pockels student‐lab was aimed to experimentally to develop and understand the principle and properties of macromolecules and to use models for explanation. Two polyelectrolytes, alginate as a natural polymer, and polyacrylate as a synthetic one are presented. Their gelling behavior is studied considering various parameters of influence systematically. Also, examples of applied research are included in the selection. The project is directed to pupils of 5–10th grade, but can be adapted for younger or older students.
Sequence‐defined oligourethanes were tested as in vivo taggants for implant identification. The oligomers were prepared in an orthogonal solid‐phase iterative approach and thus contained a coded ...monomer sequence that can be unequivocally identified by tandem mass spectrometry (MS/MS). The oligomers were then included in small amounts (1 wt %) in square‐centimeter‐sized crosslinked poly(vinyl alcohol) (PVA) model films, which were intramuscularly and subcutaneously implanted in the abdomen of rats. After one week, one month, or three months of implantation, the PVA films were explanted. The rat tissues exposed to the implants did not exhibit any adverse reactions, which suggested that the taggants are not harmful and probably not leaching out from the films. Furthermore, the explanted films were immersed in methanol, as a solvent for oligourethanes, and the liquid extract was analyzed by mass spectrometry. In all cases, the oligourethane taggant was detected, and its sequence was identified by MS/MS.
Uniforme Oligourethane mit definierten Sequenzen wurden in Filme aus quervernetztem Polyvinylalkohol eingebracht, die in lebende Ratten implantiert wurden. Nach drei Monaten wurden die markierten Filme wieder explantiert, und die Sequenzeninformation der Oligourethan‐Markierungen durch Tandem‐Massenspektrometrie eindeutig ausgelesen.
A protein‐sized (ca. 4.2×4.2×3.6 nm3) non‐biologically derived molecule {Nb288O768(OH)48(CO3)12} (Nb288) containing up to 288 niobium atoms has been obtained, which is by far the largest and the ...highest nuclearity polyoxoniobate (PONb). Particularly, in terms of metal nuclearity number, Nb288 is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb288 can be described as a giant windmill‐like cluster aggregate of six nanoscale high‐nuclearity PONb units {Nb47O128(OH)6(CO3)2} (Nb47) joined together by six additional Nb ions. Interestingly, the 47‐nuclearity Nb47 units generated in situ can be isolated and bridged by copper complexes to form an inorganic–organic hybrid three‐dimensional PONb framework, which exhibits effective catalytic activity for hydrolyzing nerve agent simulant of dimethyl methylphosphonate. The unique Nb47 cluster also provides a new type of topology to very limited family of Nb‐O clusters.
Riesengroß ist ein Polyoxoniobat (PONb) mit 288 Nb‐Zentren – das mit Abstand größte PONb und das Polyoxometallat mit der zweithöchsten Zahl an Metallatomen. Das PONb enthält eine in situ gebildete 47‐kernige Baueinheit, die durch Metallkomplexe unter Bildung eines ausgedehnten PONb‐Gerüsts stabilisiert werden kann und in der Lage ist, Dimethylmethylphosphonat zu hydrolysieren.
Membrane channels span the cellular lipid bilayers to transport ions and molecules into cells with sophisticated properties including high efficiency and selectivity. It is of particular biological ...importance in developing biomimetic transmembrane channels with unique functions by means of chemically synthetic strategies. An artificial unimolecular transmembrane channel using pore‐containing helical macromolecules is reported. The self‐folding, shape‐persistent, pore‐containing helical macromolecules are able to span the lipid bilayer, and thus result in extraordinary channel stability and high transporting efficiency for protons and cations. The lifetime of this artificial unimolecular channel in the lipid bilayer membrane is impressively long, rivaling those of natural protein channels. Natural channel mimics designed by helically folded polymeric scaffolds will display robust and versatile transport‐related properties at single‐molecule level.
Türöffner: Künstliche Transmembrankanäle werden aus selbstfaltenden formbeständigen helikalen Makromolekülen aufgebaut, die Poren in einer Lipiddoppelschicht bilden. Die Kanäle sind außergewöhnlich stabil und transportieren effizient Protonen und Kationen. Bezüglich ihrer Lebensdauer in der Lipiddoppelschicht reichen die Kanäle an natürliche Proteinkanäle heran.
The synthesis of O‐doped benzorylenes, in which peripheral carbon atoms have been replaced by oxygen atoms, has been achieved for the first time. This includes key high‐yielding ring‐closure steps ...which, through intramolecular C−O bond formation, allow stepwise planarization of oligonaphthalenes. Single‐crystal X‐ray diffraction showed that the tetraoxa derivative forms remarkable face‐to‐face π–π stacks in the solid state, a favorable solid‐state arrangement for organic electronics.
O‐dotierte Benzorylene mit Sauerstoff‐ anstelle peripherer Kohlenstoffatome wurden über intramolekulare C‐O‐Verknüpfung und stufenweise Planarisierung von Oligonaphthalinen synthetisiert. Einkristall‐Röntgenbeugungsanalysen zufolge bildet das Tetraoxa‐Derivat im Festkörper geordnete π‐Stapel, die ein Vorteil für organische Elektronik sind. PXX=Perixanthenoxanthen.
Inspiration for molecular design and construction can be derived from mathematically based structures. In the quest for new materials, the adaptation of new building blocks can lead to unexpected ...results. Towards these ends, the quantitative single‐step self‐assembly of a shape‐persistent, Archimedean‐based building block, which generates the largest molecular sphere (a cuboctahedron) that has been unequivocally characterized by synchrotron X‐ray analysis, is described. The unique properties of this new construct give rise to a dilution‐based transformation into two identical spheres (octahedra) each possessing one half of the molecular weight of the parent structure; concentration of this octahedron reconstitutes the original cuboctahedron. These chemical phenomena are reminiscent of biological fission and fusion processes. The large 6 nm cage structure was further analyzed by 1D and 2D NMR spectroscopy, mass spectrometry, and collision cross‐section analysis. New routes to molecular encapsulation can be envisioned.
Größer und größer: Ein 6 nm großer Archimedischer Kuboktaeder aus X‐förmigen Terpyridinliganden und 24 Metallionen (Zn2+ oder Cd2+) wurde hergestellt und mit Synchrotron‐Röntgenbeugung analysiert. Durch Änderungen der Konzentration oder Austausch der Gegenionen konnte ein Fusions‐Fissions‐Schaltprozess zwischen dem Kuboktaeder und einem Oktaeder ausgelöst werden.
This series presents critical reviews of the present position and future trends in modern chemical research. It contains short and concise reports on chemistry, each written by the world renowned ...experts - it is still valid and useful after 5 or 10 years. More information as well as the electronic version of the whole content available at: springerlink.com. The book will appeal to scientists and practitioners in the mentioned fields and in industry.
Sequence control in polymers, well‐known in nature, encodes structure and functionality. Here we introduce a new architecture, based on the nucleophilic aromatic substitution chemistry of cyanuric ...chloride, that creates a new class of sequence‐defined polymers dubbed TZPs. Proof of concept is demonstrated with two synthesized hexamers, having neutral and ionizable side chains. Molecular dynamics simulations show backbone–backbone interactions, including H‐bonding motifs and pi–pi interactions. This architecture is arguably biomimetic while differing from sequence‐defined polymers having peptide bonds. The synthetic methodology supports the structural diversity of side chains known in peptides, as well as backbone–backbone hydrogen‐bonding motifs, and will thus enable new macromolecules and materials with useful functions.
Die Monomersequenz in Makromolekülen äußert sich in unterschiedlichen Strukturen und Funktionen. Durch submonomere Festphasensynthese wurden nukleophile aromatische Substitutionen an Cyanurchlorid durchgeführt, um eine neue Architektur von sequenzdefinierten Polymeren mit Seitenkettendiversität und nicht‐kovalenten Wechselwirkungen zwischen den Polymerrückgraten zu entwickeln.
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