IR-Spektren der Anion-Radikale von aromatischen Mononitrilen und Elektronenübergänge zwischen Anion-Radikalen und neutralen Molekülen

Zusammenfassung Es wurden die IR-Spektren (680–2500 cm^–1) der Anion-Radikale (AR) von Benzonitril, 1- und 2-Cyannaphthalin, 9-Cyanphenanthren, 4-Cyanbiphenyl, 1-Cyanpyren und 9-Cyan-anthracen gemessen, die aus den entspr. Nitrilen und metallischem Kalium in Tetrahydrofuran (THF) erhalten wurden. Die Umwandlung der Moleküle inAR führt zur Frequenzerniedrigung der nichtebenen C-H-Deformationsschwingungen im Bereich 700 bis 800 cm^–1. Die Valenzschwingungv _CN imAR liegt im Intervall 2080–2125 cm^–1, entsprechend der erniedrigten Bindungsordnung CN imAR Die IR-Spektren im Bereich 2000 bis 2250 cm^–1 wurden zur Untersuchung der Elektronenübergänge zwischenAR und den neutralen Molekülen der Nitrile benutzt. Die Richtung der Elektronenübergänge entspricht im allgemeinen der nach HMO-Methode errechneten Energien der niedrigsten antibindenden MO in den untersuchten Nitrilen.

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IR spectra of anion-radicals of aromatic mono-nitriles, and electron transitions between anion radicals and neutral molecules

The infrared spectra (680–2500 cm^–1) are measured of the anion-radicals (AR) of benzonitrile, 1- and 2-naphthalenecarbonitriles, 9-phenanthrenecarbonitrile, 4-biphenylcarbonitrile, 1-pynitriles, 9-phenanthrenecarbonitrile, 4-biphenylcarbonitrile, 1-pyrenecarbonitrile and 9-anthracenecarbonitrile, obtained on treating the initial nitriles with metallic potassium in tetrahydrofuran. The formation of theAR leads to a decrease of the out-of-plane C–H frequencies in the region 700–800 cm^–1. The nitrile frequencies of theAR is observed in the region 2080 to 2125 cm^–1, which is in agreement with the decreased order of the CN bond (HMO). The IR-Spectra in the interval 2000 to 2250 cm^–1 are used in the study of the electron transitions between theAR and the nitrile molecules. The electron transitions in the examined nitriles are in general agreement with the energies of the first antibonding orbitals, calculated by HMO.

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Ion binding properties of poly(ethylene oxide)-based networks in dioxane and toluene

Binding constants of alkali picrates to poly(ethylene oxide)-based networks were measured spectrophotometrically in dioxane at 25 and 40°C. The networks were synthesized from aliphatic tri- or tetrafunctional isocyanates and α,ω-diamino-poly-(ethylene glycol)s. The slopes of the Klotz binding plots appear to decrease in the lower picrate concentration range, suggesting that binding of the salt becomes more difficult at high picrate content. It was shown that under saturation conditions six to seven ethylene oxide units are required to bind a sodium picrate ion pair. The affinity of the PEO-resins for the alkali picrate can be enhanced by immobilizing a poly(crown ether) in the network. A number of competition experiments for sodium picrate in toluene was also carried out to obtain the affinity of soluble ligands for alkali salts. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1819–1824, 1997     

Triblock and Radial Star-Block Copolymers Comprised of Poly(ethoxyethyl glycidyl ether), Polyglycidol,Poly(propylene oxide) and Polystyrene Obtained by Anionic Polymerization Initiated by Cs Initiators

The anionic polymerization of ethoxyethyl glycidyl ether (EEGE) initiated by cesium alkoxide was studied. The ring-opening polymerization of EEGE in the presence of cesium alkoxide of 1-methoxy-2-ethanol does not involve any side reactions. The presence of an additional alcohol leads to a significant increase of the initiator efficiency. Aqueous solutions of poly (ethoxyethyl glycidyl ether) (PEEGE) exhibit lower critical solution temperature (LCST), and the polymer solubility in water is extremely sensitive to its MW. Two novel types of block copolymers based on PEEGE were synthesized: triblock-copolymers of ABA (A′:BA′) structure, where A is the PEEGE block, A′ polyglycidol (PG) and B the polypropylene oxide (PPO) block, and A₂S (A′₂S) and A₄S (A′₄S) heteroarm stars, where S is the polystyrene block. The synthesis of the ABA block was performed by polymerization of EEGE initiated by bi-functional PPO/Cesium alkoxide macroinitiator. The PEEGE blocks were converted into PG blocks by successful cleavage of the ethoxyethyl group. Polystyrene/PEEGE and polystyrene/PG three- and five- heteroarm star copolymers were synthesized by a coupling reaction between well-defined chain-end-functionalized polystyrenes carying dendritic benzyl bromide moieties with living anionic polymers of PEEGE with one cesium alkoxide terminal group. The coupling reaction proceeds quantitatively without any side reactions, and thus series of star-branched polymers can be systematically synthesized. Polystyrenes with two or four PG arms have been obtained after the cleavage of the protecting group. The compact structure of these multi-arm star polymers and their amphiphilic character leads to the formation of nanoparticles in aqueous solution with rather uniform size distribution and a mean diameter of 15 nm.     

Investigation by means of I.R. spectroscopy of styrene oligomers containing acrylonitrile active ends

The successive addition of acrylonitrile (AN) portions to oligostyrene anionic ends was studied by means of i.r. spectroscopy. The attachment of AN to the oligostyrene active centre took place mainly across the double bond of the monomer accompanied by formation of the carbanion CHCN with characteristic absorption band at 2030–2040 cm^?1. Comparatively high temperatures of the experiments (above ?40°) provided conditions for side reactions in the polymerization. The latter were checked spectrophotometrically: cyclization according to Ziegler-Thorpe and formation of anionic centre

and proton transfer reaction between this centre and AN causing the formation of enaminonitrile structure. By study of model compounds, the band at 2110–2130 cm^?1 was assigned to the

group.     

Theoretische Betrachtung (LCAO-MO) des Mechanismus der durch Radikalanionen initiierten Polymerisation

Zusammenfassung Ein neuer Mechanismus der durch Radikalanionen initiierten Polymerisation wird diskutiert. Die theoret. Betrachtung stützt sich vor allem auf die Annahme, daß sich ein -Komplex zwischen dem Monomeren und den Radikalanionen bildet. Anhand der LCAO-MO-Näherung wird die Verteilung der Elektronendichte auf die Komponenten der -Komplexe aus Styrol und unterschiedlichen Radikalanionen Betrachtet. Es wird aufgezeigt, daß die Übertragung der Ladung vom Radikalanion zur Molekel des Styrols in allen Fällen bedeutend ist, gleichgültig ob die Elektronenaffinität des Monomeren (des Styrols) größer oder kleiner ist als die des Kohlenwasserstoffes, der dem Radikalanion zugrunde liegt.

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In the present work a new mechanism of the radical-anion initiated polymerization is being discussed. The basic assumption is the -complex formation between monomer and radicalanions. On the basis of the LCAO-MO method (Hückel approximation) the electron distribution between the components of the styrene -complex with various radical-anions is considered. It has been shown that in all cases a considerable charge transfer from the radical-anion to the styrene takes place no matter whether the electron affinity of the monomer is greater or smaller than that of the anion-radical forming hydrocarbon.

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Wechselwirkung zwischen Polyäthylenoxid und Fluorenyl-Alkalimetall-Verbindungen in Tetrahydrofuran

Ohne Zusammenfassung     

Nano-Templates from Thermoresponsive Poly(ethoxytriethyleneglycol acrylate) for Polymeric Nano-Capsules

Temperature responsive poly(ethoxytriethyleneglycol acrylate) (PETEGA) of Mn = 8000 and M_w/M_n = 2.30 was synthesized by ATRP. Dilute aqueous solutions of PETEGA exhibit lower critical solution temperature (LCST) at around 34 °C. We found that PETEGA can form nano-sized uniform colloidal aggregates (50-200 nm) above LCST either with or without an additional surfactant. Therefore PETEGA nano-aggregates were used as templates for the seeded free radical copolymerization of acrylamides or methacrylates together with a cross-linker to form acrylamide or methacrylate based core-shell particles. The formation of the PETEGA templates was investigated by dynamic light scattering (DLS) in order to find optimal conditions for obtaining narrow dispersed aggregates of desired sub-micron dimensions. Core-shell particles were characterized by DLS and scanning electron microscopy.     

Conductivity studies on living polymers with an α-oxide terminal unit in tetrahydrofuran

The dissociation constants were determined in tetrahydrofuran for “living” polymers, built of a polystyrene block and statistically one terminal unit of ethylene oxide, butylene oxide or styrene oxide using lithium, sodium and potassium as counterions. The values for the dissociation constants at 25° of the alcoholate ion pairs are of the order of 10^?9–10^?10 M. It was found that living polymers with a terminal unit of styrene oxide and a lithium or sodium counterion form ion triplets at concentrations of about 10^?5 M. Their dissociation constants, calculated by the Fuoss and Kraus method, are of the order of 10^?5 M.