bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of the mechanism of propagation and transfer reactions in the polymerization of olefins by Ziegler‐Natta catalysts, 1. Determination of the number of propagation centers and the rate constant
Authors: Chumaevskii Nikolay B. , Zakharov Vladimir A. , Bukatov Gennadii D. , Kuznetzova Galina I. , Yermakov Yurii I. 
Published: April 2003

AbstractThe number of propagation centers (Cp) and the propagation rate constant (Kp) in the polymerization of ethylene and propene in the presence of heterogeneous TiCl3 derived Ziegler‐Natta catalysts of different composition were determined using the method of quenching the polymerization by radioactive carbon monoxide (14CO). The values of Kp, (1,2±0,3)·104 l mol−1 s−1 at 75°C for ethylene and (90±20) l mol−1 s−1 at 70°C for propene polymerization, significantly exceed those ones obtained by use of tritium tagged alcohols as quenching agents. Further, for the polymerization of olefins in the presence of TiCl3 based catalysts, the influence of catalyst composition, polymerization conditions, and monomer nature on Cp and Kp was studied.
ESR measurements during γ‐radiation induced solid‐state polymerization of 1,3,5‐trithiane
Authors: Gearhart Richard C. , Schultz Jerold M. 
Published: April 2003

AbstractThe time‐dependences of ESR spectra were measured during the γ‐radiation induced solid‐state polymerization of 1,3,5‐trithiane to polythiomethylene. The reaction was carried out at several temperatures, both under air and under N2. The initial reaction kinetics are second order, but become of lower order at the highest temperatures under air. Mass spectrographic results indicate spontaneous degradation under these high temperature conditions. It is concluded that an observed peak in reaction rate with temperature derives from the onset of spontaneous chain termination.
Untersuchungen einiger gesetzmäßigkeiten der polykondensation von tetracarbonsäure‐tetranitrilen mit diaminen sowie der eigenschaften der entstehenden polymere
Authors: Winogradowa Swetlana V. , Siling Swetlana A. , Solowjöw Wladimir N. 
Published: April 2003

AbstractPolyhexazocyclane sind ein neuer Typ von Polymeren mit stickstoffhaltigen Makroheterocyclen in der Kette, die durch Polykondensation von Tetracarbonsäuretetranitrilen mit Diaminen unter Ammoniakentwicklung dargestellt werden können.Die Untersuchung einer Modellreaktion von Phthalodinitril mit p‐Phenylendiamin in verschiedenen Hydroxyl‐Gruppen enthaltenden Medien hat gezeigt, daß die Kondensation in Phenol und Kresolen im Unterschied zur Kondensation in aliphatischen Alkoholen die Darstellung von makroheterocyclischen Verbindungen mit hoher Ausbeute ermöglicht. Bei der Durchführung solcher Kondensationen in Phenolen mit elektronenanziehenden Substituenten werden keine Makroheterocyclen gebildet.Die Umsetzung von Ammoniak mit einem Modell‐Makroheterocyclus führt zur Bildung einer Reihe von Substanzen, die Zwischenprodukte seiner Synthese sind. Dies gestattet die Annahme, daß die Bildung des Makroheterocyclus und folglich die Polykondensation der Tetracarbonsäure‐tetranitrile mit Diaminen ein Gleichgewichtsprozeß ist.Die Polyhexazocyclane sind thermobeständige Polymere. Der Zersetzungspunkt an der Luft liegt über 400°C. Bei der Erhitzung über 250°C werden die Polymere vernetzt. Sie erweichen nicht vor ihrer Zersetzung.
Selective adsorption of metal ions on poly(4‐vinylpyridine) resins in which the ligand chain is immobilized by crosslinking
Authors: Nishide Hiroyuki , Tsuchida Eishun 
Published: April 2003

AbstractChelate forming resins (3) were prepared by crosslinking poly(4‐vinylpyridine) (1) with 1,4‐dibromobutane (2) and their complexation with metal ions was studied. Stability constants (K) were found to be much higher for the Cu‐3 system than for the Cu‐1 system, which indicates that 3 uptakes Cu ions with high efficiency. K and the adsorption capacity of Cu decrease largely with increasing degree of crosslinking. Visible and ESR spectra of Cu‐3 show that the structure of the Cu complex within 3 is the same as that of the monomeric Cu‐pyridine complex. However, the ligand‐chain is immobilized in the highly crosslinked 3c and 3d, so that the square planar structure of a stable Cu complex is distorted. The amount of adsorption of Cu, Fe, Cr, Ni, and Zn ions on 3 decreases with the crosslinking, but the adsorption of Hg ions is independent; i.e. 3d selectively adsorbs Hg ions. Metal complexed 1 was crosslinked according to Scheme 1 and the metal ion which was used as template is well adsorbed by the obtained 3. It is considered, therefore, that the ligand chain is maintained at the best conformation for the template ion.
Über Polyarylenalkenylene und Polyheteroarylenalkenylene, 7. Die Anwendung von HMO‐Rechnungen auf elektronenspektroskopische und struckturanalytische Probleme oligomerer und polymerer Polyarylenalkenylene und Polyheteroarylenalkenylene
Authors: Koßmehl Gerhard , Bohn Bodo , Broser Waldemar 
Published: April 2003

AbstractFür die homologen Reihen der Di‐2‐thienyl‐ und Diphenylalkapolyene mit 1—6 olefinischen Doppelbindungen sowie die oligomeren Arylen‐ bzw. 2,5‐Thienylenvinylene und 2,5‐Thienylen‐1,3‐butadienylene wurden nach der HMO‐Methode die Energiewerte für den π → π* Übergang (Δxj‐Werte) berechnet, die mit den λmax‐Werten (π → π*‐Übergänge) gut übereinstimmen. Für die genannten Verbindungen wurden auch die Bindungsordnungen für die Kohlenstoff‐Kohlenstoff‐Bindungen berechnet. Aus den berechneten Bindungsordungen für die π‐Elektronensysteme ergibt sich, daß der Bindungsangleich schon bei den Tetrameren bis Pentameren weitgehend erreicht ist. Für 5 einfache Verbindungen läßt sich anhand der röntgenographisch ermittelten Bindungslängen eine gute Übereinstimmung über die Bindungsangleichung dieser konjugierten π‐Elektronesysteme mit den Aussagen aus den Bindungsordnungen feststellen.
Characterization of the urinary polymer‐related material from rats given poly[biguanide‐1,5‐diylhexamethylene hydrochloride]
Authors: Bratt Harold , Hathway David E. 
Published: April 2003

AbstractGastro‐intestinal absorption in rats of poly[biguanide‐1,5‐diylhexamethylene hydrochloride] (1) amounts to only 5,6% of a single oral dose, and after chronic administration, tissue concentrations do not exceed 0,3 μg g−1. It has been shown by simple chromatographic and spectroscopic methods that urinary polymer‐related material consists of small amounts of 1‐oligomers, with two cyanoguanidino end groups, as well as the trace constituents, 3,3′‐dicyano‐1,1′‐hexamethylenediguanidine (8a) and a compound which is considered to be 1‐(6‐aminohexyl)‐3‐cyanoguanidine (2) that is formed during the synthesis of 1. Hence, the constituents of 1 are unmetabolized in rats.
Osmotic coefficients of aqueous polyelectrolyte solutions at low concentrations, 3. Dependence on macroion molecular weight
Authors: Oman Srečko 
Published: April 2003

AbstractEight sodium salts of polystyrenesulfonic acid (poly[1‐(sulfophenyl)ethylene]) of different molecular weights were prepared similarly and purified in the same way. Their aqueous solutions were thus chemically equivalent, and differed only in their molecular weights, which were determined viscosimetrically.The osmotic coefficients (Φ) of the acid and its sodium, thallium, calcium and cadmium salt solutions were measured by a membrane osmometer for counterion molalities mc = 10−2 to 5·10−4mol/kg, at 25°C. In the same concentration range, the activity coefficients of hydrogen counterions (γH) of acid solutions were calculated from electromotive force measurements and the osmotic coefficients of the acid solutions were determined by the cryoscopic method for two different molecular weights. The values obtained are presented graphically as functions of the measured average molecular weight for mc = 10−3 and 10−2 mol/kg and are in good mutual agreement within experimental error.This agreement of results could be assumed to verify experimentally that the colligative properties of polystyrene‐sulfonate polyelectrolytes at low concentrations are dependent on the molecular weight of the polyion.The obtained results together with some literature data, allow us to evaluate very approximately the activity coefficients of monovalent counterions (γc) for mc = 10−2 mol/kg as a function of the degree of polymerization (n) of linear oligoions or polyions, for values of n up to 104.
Radical reactions initiated by chelate complexes of transition metals, 14. Copper(II) 2‐aminoethanolate – a selective initiator for polymerization of vinyl monomers
Authors: Bartoň Jaroslav , Mapunda‐VlčKová Jana 
Published: April 2003

AbstractIt was found that copper(II) 2‐aminoethanolate (Cumea) initiates the polymerization of methyl methacrylate but not that of styrene and acrylonitrile. The selectivity of Cumea with respect to initiation of vinyl monomers is caused by formation of monomer radicals which originate from the decay of the complex Cumea‐monomer. By adding free aminoalcohol and/or carbon tetrachloride to the system Cumea‐MMA, the complex Cumea‐MMA is not formed and the initiating radicals arise from consecutive reactions between Cumea and aminoalcohol or carbon tetrachloride. In this case formation of the initiating radicals is not dependent on the complex Cumea‐monomer; consequently, a loss of selectivity of Cumea during initiation of the polymerization of unsaturated monomers occurs.
The dimerization of 1‐alkynes by rhodium(I) catalysts. Effect of phosphorus ligands on regioselectivity
Authors: Yoshikawa Susumu , Kiji Jitsuo , Furukawa Junji 
Published: April 2003

AbstractThe dimerization of 1‐alkynes by rhodium(I) complexes in the presence of phosphorus ligands is described. The products are linear and branched dimers, the ratio of which is correlated with the electronic parameters, vCO of Ni(CO)3L, of the ligands L, but no simple correlation is apparent between their steric parameter and the selectivity. Electron‐donating ligands promote the formation of the linear dimer. The substituents of the 1‐alkynes also affect the distribution of linear and branched dimers. Electron‐donating substituents prefer linear isomer to branched one. The reactivity of the substituted 1‐alkynes (RCCH) increased with substituent R in the order
The proton chemical shifts of α‐helical poly‐L‐alanine
Authors: Asakura Tetsuo , Ando Isao , Nishioka Atsuo 
Published: April 2003

AbstractThe proton chemical shifts of NH, α‐CH, and CH3 groups in α‐helical poly‐L‐alanine (PLA) were calculated by taking account of diamagnetic shielding effect, electric‐field effect, and magnetic anisotropy effect. The first and second terms were obtained from the electron density distributions in the model compounds of PLA hydrogen‐bonded with formamide, and the last term was evaluated from the magnetic anisotropy effect due to the CO, (O)CN, and α‐CHN bonds, where the two kinds of bond anisotropy of the CN bond were estimated semi‐empirically on the basis of the experimental data about six kinds of amides. The calculated chemical shifts agreed fairly well with the observed values.
Catalyses by polymer complexes, 2. Enhanced esterolytic reactivity of complexes of polymeric soaps and dodecanethiol towards 4‐nitrophenyl acetate
Authors: Shinkai Seiji , Kunitake Toyoki 
Published: April 2003

AbstractThe reaction of dodecanethiol with 4‐nitrophenyl acetate in the presence of dodecyl derivatives of poly(4‐vinylpyridine) and poly(1‐vinyl‐2‐ethylimidazole) was studied at 30°C. It was found that at pH 9,48 the reaction is completed after a few seconds in the presence of polymeric micelles with a content of dodecyl groups > 22 mole‐%, and that the second‐order rate constant amounts to 3,2·103 l mol−1 s−1, which is ca. 150 times higher than that obtained in the absence of the polymer. The reaction rate increases with the content of dodecyl groups in the polymer and the maxima appear at 20 to 30 mole‐%. Polymers substituted with hexyl or ethyl groups instead of dodecyl groups, showed to be virtually ineffective. Obviously, the hydrophobic environment of the polymer activates the bound thiol anion.
Interaction between dyes and polyelectrolytes, 5. Effect of organic and inorganic salts on metachromasy of methylene blue
Authors: Shirai Masamitsu , Nagaoka Yoshihiro , Tanaka Makoto 
Published: April 2003

AbstractThe effect of alkali metal chlorides and 1‐substituted 3‐carbamoylpyridinium bromides (2a–d) on the metachromatic behavior of methylene blue (1) induced by poly(potassium styrenesulfonate) (PSS) and poly(potassium vinyl sulfate) (PVS) was investigated spectrophotometrically. The size of hydrated ion and the hydrophobicity of substituent were significant factors for inorganic and organic salts, respectively. Effect of these salts on the metachromasy was characteristic of each polyanion used. A peculiar phenomenon that the metachromasy of the PSS‐1 system was enhanced on addition of small amounts of 1‐dodecyl‐3‐carbamoylpyridinium bromide (2d) was observed.
Application of spin trapping technique to radical polymerization, 15. Photo‐decomposition of dibenzoyl disulfide and evaluation of relative reactivities of vinyl monomers toward the benzoylthiyl radical
Authors: Sato Tsuneyuki , Abe Masao , Otsu Takayuki 
Published: April 2003

AbstractThe mechanism of photo‐decomposition of dibenzoyl disulfide (DBDS) in benzene or in monomers, and the evaluation of relative reactivities of various vinyl monomers toward the benzoylthiyl radical (4) were investigated by means of the spin trapping technique using 2‐methyl‐2‐nitrosopropane (BNO). When DBDS photo‐decomposed in benzene at 22±2°C in the presence of BNO, both 4 and benzoyl radicals were trapped as their nitroxyl radicals, indicating that both SS and CS bonds in DBDS were decomposed during its photolysis. However, when the photo‐decompositions were performed in the monomers, propagating radicals (7) were trapped, but no allyl‐type radicals (11). The coupling constants of the nitroxyl radicals of various propagating radicals were determined. From the ESR spectra of the systems DBDS/vinyl monomers/methyl methacrylate (as reference)/BNO the relative concentrations of the nitroxyls, [8]/[10, X = COOCH3], were determined by computer simulation, and the relative reactivities of the vinyl monomers toward 4 were estimated. It was found that the relative reactivities of these monomers are correlated with their e values to give a linear relationship with a negative slope, similar to those toward the tert‐butoxyl radical found in the previous paper.
Reactive copolymers of N‐(2‐hydroxypropyl)methacrylamide with N‐methacryloylated derivatives of L‐leucine and L‐phenylalanine, 1. Preparation, characterization, and reactions with diamines
Authors: Kopeček J. 
Published: April 2003

AbstractReactive copolymers of N‐(2‐hydroxypropyl)methacrylamide (1) with p‐nitrophenyl esters of N‐methacryloylglycyl‐L‐leucine (3a), N‐methacryloylglycyl‐L‐phenylalanine (3b), N‐methacryloyl‐ε‐aminocaproyl‐L‐leucine (7a), and N‐methacryloyl‐ε‐aminocaproyl‐L‐phenylalanine (7b) (i.e. copolymers 8–11) were synthesized. The polymers thus obtained were characterized by the content of active groups, by intrinsic viscosity [η], and by the rate constant of aminolysis with tert‐butylamine in dimethyl sulfoxide. Polymers containing free NH2 groups were prepared by a polymeranalogous reaction with diamines, predominantly 1,6‐hexanediamine. The effect of the copolymer structure, of diamine, and of the reaction conditions on the course of the polymeranalogous reaction was studied.
1H NMR study of random and alternating styrene/n‐alkyl methacrylate copolymers
Authors: Podešva J. , Doskočilová D. 
Published: April 2003

AbstractThe 1H NMR spectra of random and alternating copolymers of styrene and methyl methacrylate, ethyl methacrylate, butyl methacrylate, and octyl methacrylate were analyzed. In the first approximation, the one‐parameter statistics suggested for the interpretation of these spectra is in agreement with the experimental data. The way in which the copolymer is synthesized and the copolymerization mechanism following therefrom markedly affect the magnitude of the parameter of coisotacticity σ: for all comonomer pairs under study, σ is higher if an organometallic catalyst is used (alternating copolymerization) than in the case of a radical initiator (statistical copolymerization). With increasing number of carbon atoms in the n‐alkyl alcohol residue, σ decreases to a limiting value.
Das Verhalten von isotaktischen Polyacrylsäuren im Organismus. Verteilung und Ausscheidung bei Mäusen
Authors: Mück Karl‐Friedrich , Christ Othmar , Kellner Hans‐Martin 
Published: April 2003

AbstractIsopropyl acrylate‐2,3‐14C and isopropyl acrylate‐2,3‐3H were polymerized using anionic initiators. The isotactic polymers were fractionated by fractional precipitation and characterized. The polymer fractions were hydrolysed to polyacrylic acids by trifluoroacetic acid. Aqueous solutions of these radioactive labelled polyacrylic acids were injected intravenously to mice in amounts of 40 to 100mg/kg. Distribution in organs and the excretion were studied. About two thirds of the dose were excreted within the first two days with a half‐life of about 0,5 days. Further excretion took place with a half‐life of about six weeks. Distribution in the organism was not uniform; the highest concentrations were found in spleen, bones, and liver, i.e. organs being parts of the reticuloendothelial system. A relationship between organ concentration and molecular weight of the polyacrylic acid was only observed in the spleen. Nine weeks after injection about 10% of the dose were still retained in the organism, mainly in the skeleton.
Cationic polymerization of cyclic amines, 5. Polymerization of N‐tert‐butylaziridine
Authors: Bossaer Piet K. , Goethals Eric J. 
Published: April 2003

AbstractThe polymerization of N‐tert‐butylaziridine (TBA) in dichloromethane with different cationic initiators leads to quantitative conversion. With triethyloxonium tetrafluoroborate (TEFB), initiation is rapid and the molecular weights of the polymers increase with increasing [TBA]/[TEFB] ratios. In contrast with other polymerizations of N‐substituted aziridines, termination reactions are absent. This is ascribed to the high steric hindrance of the tert‐butyl group which makes a nucleophilic attack of a polymeric amino function on the growing species (aziridinium ion) impossible. Poly(TBA) obtained by precipitation from its solution shows a high degree of crystallinity as is shown by its mp of 142°C (DSC) and by its well resolved X‐ray diffraction diagram. The viscosities of aqueous solutions of the hydrochloride of poly(TBA) show typical polyelectrolyte behaviour.
Zur Taktizität von Poly(α‐methylstyrol), 4. Das 1H‐ und 13C‐NMR‐Spektrum des 1,3,3‐Trimethyl‐1‐phenylbutyllithium
Authors: Wicke Reinhard , Elgert Karl‐Friedrich 
Published: April 2003

AbstractThe structure of 1,3,3‐trimethyl‐1‐phenylbutyllithium (1b), which is a model compound for the active chain end in the polymerisation of α‐methylstyrene with butyllithium, was investigated with 1H and 13C NMR spectroscopy. The carbon‐13 chemical shift of the αC‐atom in benzene and tetrahydrofuran as solvent suggests a substantial sp2 hybridisation. The rotation of the aromatic ring around the bond (C6H5)αC is hindered at room temperature. In benzene as solvent the carbon‐13 resonances of the αC‐atom and the aromatic C‐atoms are strongly broadened. This broadening, caused by exchange reactions or 13C‐7Li‐coupling, can be interpreted by an interaction of the lithium atom with the aromatic ring. This interpretation of the 13C NMR spectra leads to a structure, in which the lithium is not located at the αC‐atom but in the space over the bond (C6H5)αC.
Zur Taktizität von Poly(α‐methylstyrol), 6. Zum stereoregulierenden Mechanismus der Polyreaktion des α‐Methylstyrols mit Butyllithium in Tetrahydrofuran
Authors: Wicke Reinhard , Elgert Karl‐Friedrich 
Published: April 2003

AbstractSome models of the stereoregulating mechanism of the polymerisation of α‐methylstyrene with butyllithium in tetrahydrofuran are discussed. A mechanism is proposed, in which the depolymerisation of the polymer chain and an isomerisation reaction of the active site change the tacticity generated by each propagation step. The isomerisation reaction is interpreted as a dissociation of the active lithiumorganic compound occurring with racemisation. The quantitative calculation of the tacticity based on the mechanism without depolymerisation using kinetic data agrees well with the experimental dependence of the tacticity on reaction temperature and initial monomer concentration. The activation parameters of the isomerisation reaction used in this treatment are (index r = racemic, m = meso):
The thermal behavior of cycloalkanes
Authors: Höcker Hartwig , Riebel Klaus 
Published: April 2003

AbstractThe thermal behavior of cycloalkanes (CH2)n with 12 ≤ n ≤ 84 prepared by metathesis reaction of cyclododecene, GPC separation of the oligomers, and hydrogenation has been investigated. The molar enthalpies of fusion being lower by a certain amount than those of the corresponding n‐alkanes are a linear function of the chain length n. The entropy of fusion per CH2 increases with chain length in a not‐linear mode (when plotted vs. 1/n). The melting points of the cycloalkanes are lower than those of the corresponding n‐alkanes, the difference becoming smaller with increasing chain length.
Synthesis and condensation polymerization of N‐(3‐carboxy‐2‐hydroxypropyl) derivatives of purine bases
Authors: Hattori Masahira , Takai Hiroshi , Kinoshita Masayoshi 
Published: April 2003

Abstract4‐(1,3‐Dimethyl‐2,6‐dioxo‐2,6‐dihydropurin‐7‐yl)‐3‐hydroxybutyric acid (4a) and 4‐(6‐amino‐9‐purinyl)‐3‐hydroxybutyric acid (4b) were synthesized through the addition reaction of theophylline or adenine, respectively, to 1‐chloro‐2,3‐epoxypropane followed by cyanization and acidic hydrolysis. Condensation polymerization of 4a was carried out using dicyclohexylcarbodiimide, 2,4,6‐triisopropylbenzenesulfonyl chloride or p‐toluenesulfonyl chloride as dehydrating agents in dimethylformamide or pyridine. The oligoester of 4a was obtained as a white powder with a molecular weight > 700, according to gel filtration measurement.
Interaction between dyes and polyelectrolytes, 8. Effect of polyanions on the mixed dimer formation of cationic dyes
Authors: Shirai Masamitsu , Nagatsuka Tatsuki , Tanaka Makoto 
Published: April 2003

AbstractThe effect of polyanions on the formation of mixed dimers of methylene blue (1) and trypaflavine (2), methylene blue (1) and phenosafranine (3), and methylene blue (1) and pyronine G (4) was investigated spectrophotometrically. The following polyanions were used: poly(potassium styrenesulfonate) (PSS), poly(potassium vinyl sulfate) (PVS), and poly(sodium acrylate) (PAA). On addition of polyanions, the formation of mixed dimers was enhanced largely. Thermodynamic parameters inferred that the enhancement of the formation of mixed dimers in the presence of polyanions resulted from an entropic factor.
Polymerization of lactams, 24. Effect of impurities on the non‐activated polymerization of 2‐pyrrolidone initiated with potassium tert‐butoxide
Authors: Roda Jan , Kmínek Ivan , Králíček Jaroslav 
Published: April 2003

AbstractThe effect of tert‐butyl alcohol, lower alcohols, and water on the non‐activated polymerization of 2‐pyrrolidone initiated with potassium tert‐butoxide at 40°C was investigated. It was proved that the alcoholytic activity of alcohols decreased with the steric hindrance of the hydroxyl group; the effect of water is distinctly more pronounced.