Search results for "polymer chemistry"
showing 10 items of 3410 documents
Acid‐Cleavable Poly(ethylene glycol) Hydrogels Displaying Protein Release at pH 5
2020
Abstract PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring‐opening copolymerization of ethylene oxide with 3,4‐epoxy‐1‐butene (EPB) and subsequent modification to introduce acid‐degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross‐linking. Copolymers with different molar ratios of EPB, molecular weights (M n) up to 10 000 g mol−1 and narrow dispersities (Đ<1.05) were prepared. Both the P(EG‐co‐isoEPB)MA copolymer and the hydrogels showed pH‐…
Stabilized Naked Sub-nanometric Cu Clusters within a Polymeric Film Catalyze C-N, C-C, C-O, C-S, and C-P Bond-Forming Reactions
2015
[EN] Sub-nanometric Cu clusters formed by endogenous reduction of Cu salts and Cu nanoparticles are active and selective catalysts for C−N, C−C, C−O, C−S, and C−P bond-forming reactions. Sub-nanometric Cu clusters have also been generated within a polymeric film and stored with full stability for months. In this way, they are ready to be used on demand and maintain high activity (TONs up to 104 ) and selectivity for the above reactions. A potential mechanism for the formation of the sub-nanometric clusters and their electronic nature is presented.
Synthesis, structural diversity, inter-conversion and reactivity of Cu(II) complexes of hydroxy-rich molecules
2002
Tetranuclear Cu(II) complexes having linear, cubane and pseudodouble-cubane cores were synthesized using hydroxy-rich molecules possessing amine and imine groups. The products were structurally characterized and were studied for their ability to oxidize catechol as well as for their inter-conversion between mono- and tetra-nuclear complexes.
Synthesis, Characterization, and Electrochemistry of Open-Chain Pentapyrroles and Sapphyrins with Highly Electron-Withdrawing meso -Tetraaryl Substit…
2017
International audience; A series of open-chain pentapyrroles and sapphyrins with highly electron-withdrawing substituents (i.e., CN, CF3 , or CO2 Me) on the meso-phenyl rings was synthesized and characterized as to the spectral properties, protonation reactions, and electrochemistry in non-aqueous media. The investigated compounds are represented as (Ar)4 PPyH3 and (Ar)4 SapH3 where PPy and Sap correspond to the tri-anion of the open-chain pentapyrrole and sapphyrin, respectively, and Ar=p-CNPh, p-CF3 Ph, or p-CO2 MePh. UV/Vis and 1 H NMR spectroscopy as well as mass spectrometry data are given for the confirmation of the structures for the newly synthesized compounds. An X-ray structure fo…
1966
Die spontane Autoxydation N,N-dialkylierter Arylamine verlauft langsam. Sie wird durch Essigsaure, Azoisobuttersauredinitril (AIBN), Kobaltverbindungen, Benzylchlorid und Essigsaureanhydrid beschleunigt. Essigsaureanhydrid uberfuhrt die als Inhibitoren sehr wirksamen, durch oxydative Entalkylierung entstandenen sek. Amine in die als Inhibitoren wirkungslosen N-Acetylderivate (Ausbeute bis 90%). Die bei der Autoxydation als Kettentrager wirksamen Aminohydroperoxyde I konnen (a) durch Kondensation in die Dialkylperoxyde II ubergefuhrt und (b) durch Triphenylphosphin desoxygeniert werden. Die Amindialkylperoxyde II lassen sich in Substanz aus den Autoxydationsansatzen isolieren. AIBN lost unte…
Über die homogene und heterogene acetylierung von polyformaldehyd. 28. Mitteilung über polyoxymethylene1
1966
Die Acetylierung der Endgruppen eines hochmoleckularen Polyoxymethylendiols mit Essigsaureanhydrid wurde bei 200°C in Substanz sowie bei 135°C in Losung und in Suspension untersucht. Die Umsetzung ist in homogenem Medium innerhalb kurzer Zeit praktisch vollstandig; bei 200°C erfolgt jedoch ohne Zusatz eines (tertiaren) Amins eine besonders starke Verminderung der Molekulargewichte und ein Verlust an Polymerem durch Bildung flussiger Oligo-oxymethylendiacetate. Eine fast quantitative Acetylierung ohne Molekulargewichtsverminderung ist durch Umsetzung bei 135°C in Losung unter Zusatz eines tertiaren Amins moglich. Die Veresterungsgeschwindigkeit bei 135°C ist in heterogenem Medium wesentlich …
Zur protonenkatalysierten Aralkylierung von 1,2,3-Trimethylindol und 1,2,3,4-Tetrahydrocarbazol mit Arylaldehyden
1987
1,2,3-Trimethylindol (2) liefert mit Benzaldehyden die Kondensationsprodukte 5 und 6, wahrend aus den NH-Indolen 1 und 3 die Verbindungen 7 und 8 entstehen. Proton-catalyzed Aralkylation of 1,2,3-Trimethylindole and 1,2,3,4-Tetrahydrocarbazole with Arylaldehydes Reaction of 1,2,3-trimethylindole (2) with benzaldehydes leads to the condensation compounds 5 and 6, the NH-indoles 1 and 3, however, give 7 and 8.
Double Thermoresponsive Block Copolymers Featuring a Biotin End Group
2010
A poly(oligo(ethylene glycol) monomethyl ether methacrylate)-block-poly(N-isopropyl methacrylamide) (POEGMA-b-PNIPMAM) block copolymer with a biotin end group on the PNIPMAM block as a biotarget was synthesized as a model system for temperature-controlled polymer immobilization. The synthesis was based on RAFT polymerization followed by postpolymerization modification of an activated ester precursor block and an exchange of the dithioester end group within one step. NMR, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and turbidimetry measurements were performed to investigate the stimulus-responsive properties. The double thermoresponsive POEGMA-b-PNIPMAM with biot…
Anionic Polymerization of (Meth)acrylates in the Presence of Cesium Halide−Trialkylaluminum Complexes in Toluene
2001
The polymerization of methyl methacrylate and various acrylates initiated by ester enolates in the presence of cesium halide-trialkylaluminum complexes, Cs[Al n R 2n X] (n = 1, 2; R = Et, Bu'), in toluene has living and controlled character at -20 °C for methacrylates (X = Cl) and at -65 °C for n-butyl acrylate (X = F). Quantitative monomer conversions are usually reached, leading to polymers with narrow molecular weight distributions (M w /M n < 1.1). Kinetic investigations indicate a rather complex polymerization mechanism, and we assume an equilibrium between at least two active species. With this new initiating system, beside acrylate homopolymers, random and graft copolymers can be syn…