0000000000161172
AUTHOR
Jana Herzberger
Poly(THF-co-cyano ethylene oxide): Cyano Ethylene Oxide (CEO) Copolymerization with THF Leading to Multifunctional and Water-Soluble PolyTHF Polyelectrolytes
Cyano-functional polyether copolymers based on THF were prepared via cationic ring-opening copolymerization of THF with cyano ethylene oxide (CEO). The CEO content of poly(tetrahydrofuran) (polyTHF) based copolymers varied from 3.3 to 29.3%, and molecular weights ranged from 5100 to 31900 g·mol–1 with Mw/Mn in the range of 1.31 to 1.74 (SEC in THF, PS standards). The polymerization was conducted with methyl trifluoromethanesulfonate (MeOTf) as an initiator. Kinetic studies concerning incorporation of both monomers were performed via NMR spectroscopy. The cyano groups at the poly(THF-co-CEO) copolymers enable direct access to amino (polyTHF–NH2) and carboxyl groups (polyTHF–COOH) in facile o…
Epicyanohydrin: Polymerization by Monomer Activation Gives Access to Nitrile-, Amino-, and Carboxyl-Functional Poly(ethylene glycol)
Both homo- and copolymerization of the hitherto nonpolymerizable epoxide monomer epicyanohydrin (EPICH) with ethylene oxide (EO) have been studied, employing the monomer activation technique. Tetraoctylammonium bromide or tetrabutylammonium iodide was used as initiator combined with i-Bu3Al to activate the EPICH monomer. The EPICH content was varied from 4 to 16 mol %, yielding well-defined PEG-co-PEPICH copolymers with molecular weights Mn (SEC) ranging from 3700 to 8800 g mol–1. The nitrile groups of the resulting polyethers were further reduced or hydrolyzed to introduce amino, amide, or carboxyl groups at the polyether backbone, circumventing protecting group chemistry. Successful trans…
Thioether-Bearing Hyperbranched Polyether Polyols with Methionine-Like Side-Chains: A Versatile Platform for Orthogonal Functionalization
The synthesis of thioether-bearing hyperbranched polyether polyols based on an AB/AB2 type copolymerization (cyclic latent monomers) is introduced. The polymers are prepared by anionic ring-opening multibranching copolymerization of glycidol and 2-(methylthio)ethyl glycidyl ether (MTEGE), which is conveniently accessible in a single etherification step. Slow monomer addition provides control over molecular weights. Moderate dispersities (Đ = 1.48–1.85) are obtained, given the hyperbranched structure. In situ 1H NMR copolymerization kinetics reveal reactivity ratios of rG = 3.7 and rMTEGE = 0.27. Using slow monomer addition, copolymer composition can be systematically varied, allowing for th…
Die lebende anionische Polymerisation
Zusammenfassung Vor sechzig Jahren entdeckte Michael Szwarc die lebende anionische Polymerisation. Trotz ihrer hohen synthetischen Anforderungen ist sie bis heute die praziseste Methode zur Herstellung von wohldefinierten Polymeren und inspirierte zahlreiche neue Polymerisationsmethoden. Masgeschneiderte Blockcopolymere finden sich in den verschiedensten Anwendungen von High-End-Verpackungsmaterialien uber die Elektronik bis hin zu Nanomedizin.
Intrinsic superoxide dismutase activity of MnO nanoparticles enhances the magnetic resonance imaging contrast
Superoxide radicals are associated with the development of many severe diseases, such as cancer. Under nonpathogenic conditions, the natural enzyme superoxide dismutase (SOD) regulates the intracellular superoxide concentrations, but nearly all tumor tissues show reduced SOD levels. Selective imaging in early progression stages remains a key requirement for efficient cancer diagnosis and treatment. Magnetic resonance imaging (MRI) as a noninvasive tool with high spatial resolution may offer advantages here, but MRI contrast agents exhibiting a redox-triggered change in the image contrast towards superoxide radicals have not been reported so far. Here we show that manganese oxide (MnO) nanop…
Iron Oxide Superparticles with Enhanced MRI Performance by Solution Phase Epitaxial Growth
Organized three-dimensional (3D) nanomaterial architectures are promising candidates for applications in optoelectronics, catalysis, or theranostics owing to their anisotropy and advanced structural features that allow tailoring their physical and chemical properties. The synthesis of such complex but well-organized nanomaterials is difficult because the interplay of interfacial strain and facet-specific reactivity must be considered. Especially the magnetic anisotropy with controlled size and morphology plays a decisive role for applications like magnetic resonance imaging (MRI) and advanced data storage. We present a solution phase seed mediated synthesis of colloidal, well dispersible ir…
Stimuli-Responsive Tertiary Amine Functional PEGs Based on N,N-Dialkylglycidylamines
Amine-functional poly(ethylene glycol) (PEG) copolymers have been prepared that exhibit thermo- and pH- responsive behavior in aqueous solution. Three novel tertiary di(n-alkyl)glycidylamine monomers have been introduced for anionic ring-opening copolymerization (AROcP) with ethylene oxide (EO): N,N-di(n-butyl)glycidylamine (DButGA), N,N-di(n-hexyl)glycidylamine (DHexGA), and N,N-di(n-octyl)glycidylamine (DOctGA). Via controlled AROcP we synthesized well-defined (Mw/Mn = 1.05–1.14), water-soluble block- and gradient-type PEG copolymers, containing up to 25 mol % of the respective dialkylglycidylamine comonomer. Molecular weights ranged from 4900 to 12 000 g mol–1. Detailed in-situ 1H NMR ki…
Hierachical Ni@Fe2O3superparticles through epitaxial growth of γ-Fe2O3nanorods on: In situ formed Ni nanoplates
One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mossbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 …
Oxidation-responsive and "clickable" poly(ethylene glycol) via copolymerization of 2-(methylthio)ethyl glycidyl ether
Poly(ethylene glycol) (PEG) is a widely used biocompatible polymer. We describe a novel epoxide monomer with methyl-thioether moiety, 2-(methylthio)ethyl glycidyl ether (MTEGE), which enables the synthesis of well-defined thioether-functional poly(ethylene glycol). Random and block mPEG-b-PMTEGE copolymers (Mw/Mn = 1.05-1.17) were obtained via anionic ring opening polymerization (AROP) with molecular weights ranging from 5 600 to 12 000 g·mol-1. The statistical copolymerization of MTEGE with ethylene oxide results in a random microstructure (rEO = 0.92 ± 0.02 and rMTEG E = 1.06 ± 0.02), which was confirmed by in situ 1H NMR kinetic studies. The random copolymers are thermorespon…
Conventional Oxyanionic versus Monomer-Activated Anionic Copolymerization of Ethylene Oxide with Glycidyl Ethers: Striking Differences in Reactivity Ratios.
Detailed understanding of the monomer distribution in copolymers is essential to tailor their properties. For the first time, we have been able to utilize in situ 1H NMR spectroscopy to monitor the monomer-activated anionic ring opening copolymerization (AROP) of ethylene oxide (EO) with a glycidyl ether comonomer, namely, ethoxy ethyl glycidyl ether (EEGE). We determine reactivity ratios and draw a direct comparison to conventional oxyanionic ROP. Surprisingly, the respective monomer reactivities differ strongly between the different types of AROP. Under conventional oxyanionic conditions similar monomer reactivities of EO and EEGE are observed, leading to random structures (rEO = 1.05 ± 0…
“Clickable PEG” via anionic copolymerization of ethylene oxide and glycidyl propargyl ether
A straight forward synthesis of poly(ethylene glycol) (PEG) with multiple alkyne groups distributed along the polymer chain is introduced. Direct access to clickable PEG is achieved by the monomer-activated anionic ring-opening copolymerization (AROP) of ethylene oxide (EO) with glycidyl propargyl ether (GPgE). Notably for successful polymerization no protection of the alkyne unit is required owing to the mild reaction conditions. Defined PEG-co-PGPgE and PGPgE (co)polymers with PDIs of 1.18–1.60 and molecular weights of Mn = 3000–9500 g mol−1 were prepared. In situ1H NMR kinetic studies revealed remarkably disparate reactivity ratios of rEO = 14.8 and rGPgE = 0.076, representing a pronounc…
Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation.
The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazen…
Pd@Fe2O3 Superparticles with Enhanced Peroxidase Activity by Solution Phase Epitaxial Growth
Compared to conventional deposition techniques for the epitaxial growth of metal oxide structures on a bulk metal substrate, wet-chemical synthesis based on a dispersible template offers advantages such as low cost, high throughput, and the capability to prepare metal/metal oxide nanostructures with controllable size and morphology. However, the synthesis of such organized multicomponent architectures is difficult because the size and morphology of the components are dictated by the interplay of interfacial strain and facet-specific reactivity. Here we show that solution-processable two-dimensional Pd nanotetrahedra and nanoplates can be used to direct the epitaxial growth of γ-Fe2O3 nanoro…