Search results for "ionic"

ChemInform Abstract: Synthesis, Structures and DFT Calculations on Alkaline-Earth Metal Azide-Crown Ether Complexes.

2008

The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including 1-, -1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)]1/3 MeOH contains dinuclear cations with three -1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional th…

When Chlorides are the Most Reactive: A Simple Route towards Diverse Mono- and Dicationic Dimethyl Phosphate Ionic Liquids

2014

Structurally diverse aromatic and aliphatic ionic liquids have been prepared via anion metathesis utilizing alkylammonium chlorides and trimethyl phosphate. Excellent oxygen-containing functional-group tolerance in preparation of potentially greener dimethyl phosphate ionic liquids has been demonstrated. For the first time, this method has been employed in the synthesis of dicationic imidazolium-based ionic liquids possessing a dimethyl phosphate counterion, providing a simple, direct route towards structurally novel products of high purity.

1991

Telechelic α,ω-macrozwitterions — narrowly distributed polystyrene chains oppositely charged at each end — were synthesized via anionic polymerization using direct functionalization with the initiator and the termination agent. The resulting products were purified (zwitterion content ≥ 0,95) and characterized with gel permeation chromatography, viscometry, static and dynamic light scattering and small-angle neutron scattering. In unpolar solvents as toluene, the polymeric zwitterions form clusters with molecular weights depending on concentration. In the dilute case, the clusters are relatively small and consist of approximately 8 zwitterions. The structure of these clusters is discussed by…

ChemInform Abstract: Multifunctional Poly(ethylene glycol)s

2011

In the rapidly evolving multidisciplinary field of polymer therapeutics, tailored polymer structures represent the key constituent to explore and harvest the potential of bioactive macromolecular hybrid structures. In light of the recent developments for anticancer drug conjugates, multifunctional polymers are becoming ever more relevant as drug carriers. However, the potentially best suited polymer, poly(ethylene glycol) (PEG), is unfavorable owing to its limited functionality. Therefore, multifunctional linear copolymers (mf-PEGs) based on ethylene oxide (EO) and appropriate epoxide comonomers are attracting increased attention. Precisely engineered via living anionic polymerization and d…

Üuber die kationische polymerisation von äthylensulfid, initiiert durch SO3

1971

SO3 verursacht eine heftige Polymerisation von Athylensulfid in wasserfreien, inerten organischen Losungsmitteln. Die kinetischen Daten, die chemische Analyse der Endgruppen und die IR-spektroskopische Untersuchung des Polymerisats sprechen gegen eine Cokatalyse und fur einen direkten zwitterionischen Initiierungsschritt unter Bildung von Die kationischen aktiven Zentren werden rasch durch Reaktion mit den Sulfidgruppen des Oligomeren unter Bildung nicht wachstumsfahiger, acyclischer Sulfoniumionen desaktiviert; dadurch bleiben die kinetischen Kettenlangen klein, und es entsteht ein verzweigtes oder vernetztes, unlosliches Produkt. SO3 is a vigorous initiator of the cationic polymerization …

Mechanical Properties of Composite SPEEK Polymer Membranes Modified with Ionic Liquids

2015

In this work, the mechanical properties of sulphonated polyetheretherketone (SPEEK) membranes impregnated with 3 different ionic liquids (1-butyl-2,3-dimethyl- imidazolium dimethylphosphate ([BMMIM][Me2PO4])), 1,2,3-trimethylimidazolium dimethylphosphate ([MMMIM][Me2PO4])), 1,3-dimethylimidazolium dimethylphosphate ([MMIM][Me2PO4])) have been investigated. Prepared SPEEK/ionic liquid composite membranes are characterized by mechanical testing both in room and elevated temperatures. It was found that the stiffness and tensile strength of composites decreased by increasing the content of ionic liquid and the length of alkyl radical in ionic liquid as well as by increasing the temperature.

Electrochemical production of initiators for polymerization processes

2007

The most important technological interest in initiator production lies, in the electrosynthesis of complex catalytic systems, i. e. coordination compounds and Ziegler-Natta catalysts, although the choice of olefins to be polymerized with these electrosynthesized complexes is still limited to ethylene and to very few other monomers.

1977

Methacryloyloxyalkyltrimethylammonium chlorides (1a–c) with different alkyl chain lengths were synthesized and polymerized radically with 4,4′-azobis(4-cyanovalerianic acid) and K2S2O8 as initiators. With K2S2O8 as initiator, reaction orders of 0,5 and 1 with respect to initiator and monomer, were found. For the ionic monomers with longer alkyl chains the ratio of rate constants kp(2fkd/kt)0,5 was determined over a wide concentration range. It was found that with decreasing monomer concentration the ratio of rate constants increases, which is caused by a diminished termination rate because of an increased electrostatic repulsion of the ionic polymer radicals in dilute solution (increase of …

Rotationsdispersion bei monomerem und polymerem L-(–)-Lactid

1965

Bei der kationischen Polymerisation von L-Lactid entsteht ein hochkristallines, isotaktisches Polymeres. Physikalische Eigenschaften des Monomeren und Polymeren werden mitgeteilt. Fur die Rotationsdispersion von L-Lactid in verschiedenen Losungsmitteln gilt die eintermige DRUDE-Gleichung. Das Polymere hat eine Dispersions-Kurve mit einem ersten Extremum bei 275 mμ. Die Dispersionskurve des Poly-L-lactids last sich durch die MOFFITT-YANG-Gleichung beschreiben. Hieraus werden Schlusse auf die Sekundarstruktur des gelosten Polymeren gezogen. In the cationic polymerization of L-lactide a high cristalline isotactic polymer is obtained. Physical properties of monomer and polymer are reported. The…

Über die polymerisation bei der sublimation des trioxans. 17. Mitt. Über polyoxymethylene

1962

Bei der Sublimation von gereinigtem Trioxan und bei seiner Kristallisation aus der Schmelze erfolgt in der kristallinen Phase eine langsame Polymerisation zu hochmolekularem Polyoxymethylen. Die Ausbeuten an Polymeren sind um so hoher, je trockener das Trioxan ist und je geringer der Fremdgasdruck bei der Sublimation ist. Es wurde festgestellt, das diese Polymerisation durch Spuren von monomerem Formaldehyd ausgelost wird; wenn letzterer durch Silberoxyd zerstort wird, kann Trioxan unverandert sublimiert und kristallisiert werden. Wahrend der Polymerisation wird monomerer Formaldehyd von den wachsenden Polyoxymethylenketten abgespalten und so der Polymerisationskatalysator regeneriert. Desh…