bluuebunny/crossref_metadata_2025_split huggingface dataset:
Umsetzung von benzoesäureglycidylester mit primären und sekundären aminen in alkohol als lösungsmittel
Authors: Fiala Vladimír , Lidařík Miloslav 
Published: April 2003

AbstractDie Umsetzung von Benzoesäureglycidylester mit aliphatischen, aromatischen und heterocyclischen primären und sekundären Aminen in Gegenwart von Isobutylalkohol wurde studiert. Die Reaktion der Glycidylverbindungen mit Aminen verläuft nach einem termolekularen Mechanismus. In Alkohol als Lösungsmittel wird ein pseudobimolekularer Reaktionsverlauf ermittelt. Die basische Dissoziationskonstante des Amins kann zur Bestimmung der approximativen Geschwindigkeitskonstante der Benzoesäureglycidylester‐Amin‐Reaktion verwendet werden. Eine größere Abweichung von der Abhängigkeit zwischen der Dissoziationskonstante des Amins und der Geschwindigkeitskonstante der Umsetzung wurde beim Benzylamin gefunden. Die Aktivierungsenergie für die Reaktion von Benzoesäureglycidylester mit Aminen wurde bestimmt.
Crystallization of ethylene/vinylacetate random copolymers
Authors: Okui Norimasa , Kawai Toru 
Published: April 2003

AbstractIt may be anticipated that uncrystallizable units, if introduced randomely into a crystallizable polymer chain, might strongly prohibit the chain folding and enhance intermolecular crystallization, which will give rise to the fringed micelle structure. In anticipation of this, crystallization and resultant texture were studied for random copolymers of ethylene (E) and vinyl acetate (VAc) as functions of composition and crystallization temperature. Crystallization was carried out isothermally from solution as well as from melt. DTA melting behavior of the melt‐crystallized samples revealed that two types of crystals with different melting temperatures were formed during the isothermal crystallization of the copolymers. Since the height of the peak appearing at the higher temperature T1 decreased and that at the lower temperature T2 increased with the increasing VAc content and crystallization temperature, the former peak may be assigned to the chain folded crystals and the latter to the bundle‐like crystals. In other words, the transition from the chain folding crystallization to the bundle‐like crystallization did not occur sharply at a given composition as expected but the two types of crystallization coexist in a rather wide range of compositions, depending on the crystallization temperature.It became also apparent that molecular fractionation occurred during the isothermal crystallization with respect to the composition of the copolymer. Electron microscopy could not confirm the existence of the bundle‐like crystals, probably due to the fact that the individual bundle‐like crystal was not large enough to be distinguished from much larger chain‐folded lamellae with more definite shapes. On the other hand, solution grown crystals gave a single melting peak and a single X‐ray long spacing, suggesting only the chain folding crystallization occurred in the whole range of compositions studied. Molecular fractionation was again evident and the material left uncrystallized in the solution increased with the VAc content. These results may imply that the intermolecular bundle‐like crystallization depends strongly on the probability of finding other chain molecules around a given molecule. The X‐ray crystallinity as well as the heat of fusion measured suggest that the thickness of the amorphous surface layer (loose loops) of the solution grown crystals increases with the VAc content.
Rare gas plasma polymerization of benzene at −196°C
Authors: Hollahan John R. 
Published: April 2003

AbstractBenzene has been polymerized in the solid state at −196°C by a radiofrequency plasma of helium. The resulting polymer shows no sign of aromaticity. Infrared spectra suggest the polymer is a branched, aliphatic hydrocarbon polymer with some unsaturation and crosslinking. The formation of the polymer is best explained by the cission of a bond in the benzene molecule with the formation of the 1.3.5‐hexatriene biradical which polymerizes.
Molecular characterization of polyacrylonitrile polymerized by gamma‐ray irradiation
Authors: Kamide Kenji , Terakawa Toshikazu 
Published: April 2003

AbstractPolyacrylonitrile prepared by gamma‐ray irradiation to urea‐canal complex of acrylonitrile (U‐PAN) was fractionated from a solution in dimethylsulfoxide (DMSO) at 25°C, using toluene as a precipitant. Viscosities of fractions, thus prepared, in DMSO and in ethylenecarbonate (EC), were measured for elucidating the unperturbed‐chain dimensions together with the long‐range polymer/solvent interaction parameter. In conclusion, U‐PAN which is comparatively isotactic has almost the same value (the K value is 2.95·10−3) of the unperturbed‐chain dimensions as the atactic polyacrylonitrile prepared by conventional, radical polymerization (R‐PAN), whilst the long‐range parameter of U‐PAN is extremely smaller than R‐PAN in a poor solvent. The conclusions reached from these experimental facts are in very good consistence with those of other polymers with less difference in the stereoregularity.
Light scattering of polymethylmethacrylate solutions in binary solvent mixtures. Part 2. In acetone/benzene mixtures
Authors: Fujishige Shoei , Elias Hans‐Georg 
Published: April 2003

AbstractAn isotactic and an atactic polymethylmethacrylate have been investigated by light scattering measurements at 25°C in acetone/benzene mixtures in order to see the effects of the difference in the microstructures between the two stereoisomers on the preferential solvation and some other molecular parameters of the polymers. The extreme differences due to the structural effects between the stereoregular and the stereoirregular polymers appear in the mixed solvents with higher content of acetone.
Untersuchung der von anionen‐radikalen aromatischer kohlenwasserstoffe initiierten methylmethacrylat‐polymerisation mit hilfe der infrarotspektroskopie
Authors: Panayotov I. M. , Rashkov I. B. , Berlinova I. V. 
Published: April 2003

AbstractDie von Anionen‐Radikalen der aromatischen Kohlenwasserstoffe Biphenyl, Naphthalin, 2‐Phenylnaphthalin, Phenanthren, Anthracen und Acenaphthalin initierte Methylmethacrylat‐Polymerisation wurde mit Hilfe der IR‐Spektroskopie untersucht. Aus den IR‐Spektren der Reaktionsgemische sowie aus den UV‐Spektren der Polymeren wurden Schlußfolgerungen über den Initiierungsmechanismus gezogen.
Etude du mécanisme des polymérisations amorcées par les métaux alcalino‐terreux. II. Etude de la copolymérisation du styrène et du méthacrylate de méthyle
Authors: Mathis Claude , François Bernard 
Published: April 2003

AbstractDans cet article nous présentons différents résultats qui concernent la copolymérisation du styrène et du méthacrylate de méthyle amorcée par le calcium, le strontium et le baryum en milieu polaire et non polaire. Nous avons déterminé la composition des produits formés en fonction de la composition initiale des monomères et du taux de conversion. En milieu polaire le copolymère formé au début de la copolymérisation est riche en styrène. Nous avons par ailleurs mis en évidence la formation de copolymères séquencés dont l'une des séquences est constituée par du polyméthacrylate de méthyle et l'autre par un enchaǐnement statistique de styrène et de méthacrylate de méthyle. Les séquences de polyméthacrylate de méthyle présentent un nombre de triades isotactiques plus élevé qu'un homopolymère préparé dans les měmes conditions expérimentales. Ces résultats permettent de conclure à l'existence simultanée d'un mécanisme de type anionique et d'un mécanisme de type radicalaire lors de la polymérisation du méthacrylate de méthyle et de sa copolymérisation avec le styrène en présence des métaux alcalino‐terreux.
Synthèse et caractérisation de copolymères séquencés polyoxyéthylène/poly‐ε‐caprolactone
Authors: Perret Rémi , Skoulios Antoine 
Published: April 2003

AbstractOn a montré que les fonctions terminales d'un polyoxyéthylèneglycol disodé sont capables d'amorcer la polyaddition de l'ε‐caprolactone. On a préparé de cette manière une série de copolymères triséquencés poly‐ε‐caprolactone/polyoxyéthylène/poly‐ε‐caprolactone, comportant des séquences de longueur variée.Les échantillons ont été fractionnés à 34°C par addition progressive d'isooctane à leur solution dans le benzène. Les différentes fractions ont été caractérisées par osmométrie, tonométrie, dosage chimique des extrémités des chaǐnes macromoléculaires, résonance magnétique nucléaire et analyse chimique élémentaire.On a montré que les copolymères synthétisés contenaient au départ des quantités appréciables de poly‐ε‐caprolactone homopolymère de masse moléculaire peu élevée, mais qu'il était facile de les en débarrasser par simple précipitation fractionnée.
Syntheses and reactions of ferrocene‐containing polymers. V. Polymerization of ethinylferrocene
Authors: Nakashima Toshihide , Kunitake Toyoki , Aso Chuji 
Published: April 2003

AbstractPolymerizations of ethinylferrocene were carried out with ZIEGLER‐type catalysts. AlR3‐TiCl4 catalysts gave predominantly cyclic trimers, i.e., 1.2.4‐ and 1.3.5‐triferrocenylbenzene, and AlR3‐Ti(OBu)4 catalysts gave linear polymers of comparatively low molecular weight (1000‐3500). Basic organic additives like pyridine or triethylamine showed limited influence on the yield and the product distribution. The polyene may contain some irregular structures. On the other hand, polyethinylferrocene obtained by dehydrative condensation of acetylferrocene was shown by NMR spectroscopy to contain considerable amounts of aliphatic hydrogen.
Radical reactions initiated by chelate complexes of transition metals. VII. Effect of some copper chelates on the decomposition of cumene hydroperoxide in benzene
Authors: Bartoň J. , Horanská V. 
Published: April 2003

AbstractThe kinetics of cumene hydroperoxide (CHP) decomposition in benzene in the presence of bis‐(‐)‐ephedrine copper(II) chelate (Cueph), copper acetylacetonate (Cuac), and copper oxinate (Cuox) was studied by chemical analysis, UV, and ESR measurements. It was found that only Cueph markedly accelerated the CHP decomposition. The course of the CHP decomposition in presence of Cueph may be described by the kinetic equation for bimolecular reactions. From the temperature dependence an activation energy of 17.3 kcal· mole−1 for CHP decomposition has been calculated. For the decay of paramagnetic Cu2⊕ particles concentration during CHP decomposition in the presence of Cueph a reaction order of 1.1 with respect to [CHP] and 0.35 order kinetics for [Cueph] as well as an activation energy of 13.2 kcal·mole−1 were established. It was found on the basis of UV spectroscopy that during CHP decomposition in the presence of Cueph a complex between CHP and Cueph as an intermediate product was formed. Thus for the equilibrium constant of complex formation a value of 32 1 · mole−1 was estimated. The kinetic results obtained have been explained on the basis of supposition that a regeneration cycle for cupric species is operative. The disagreement between the supposed existence of the regeneration cycle and the observed decay of paramagnetic Cu2⊕ particles in the course of CHP decomposition in the presence of Cueph is the discussed.
Molecular weight distribution of “living” polymers generated by a bifunctional initiator
Authors: Höcker Hartwig 
Published: April 2003

AbstractDifferent rates of initiation and propagation, e.g., in the case of living polymerization, lead to considerable deviations from a POISSON distribution. Using a bifunctional initiator the distribution obtained is composed of a single distribution and a coupled distribution. The maximum value of x̄w/x̄n never exceeds 1.4 even for a ratio kp/ki = 106.
Untersuchungen von ordnungszuständen in DNA‐Lösungen mit hilfe der lichtstreuung
Authors: Gruber Erich , Gruber Rosl , Schurz Josef 
Published: April 2003

AbstractAus der Winkelabhängigkeit der Lichtstreuung von salzhaltigen DNA‐Lösungen kann auf das Vorliegen von Fernordnungen in der Lösung geschlossen werden. Diese Ordnung bildet sich in den ruhenden Lösungen im Verlauf mehrerer Stunden bis Tage aus. Sie kann durch Rühren gestört werden und verschwindet in der Nähe der Schmelztemperatur der DNA.Aus den gemessenen Extremwerten der Streufunktion läßt sich formal ein BRAGGscher Wert von 6000 Å errechnen, aber auch Periodizitäten von 2000 Å bzw. 3300 Å sind möglich. Zwischen 1 · 10−4 bis 3 · 10−4 g/ml läßt sich keine eindeutige Abhängigkeit von der Konzentration feststellen, wodurch man hier ein einfaches Parallelstranggitter ausschließen kann. Unmittelbar nach der Filtration durch Flächenfilter der Porenweite 0,5 μm zeigen die DNA‐Moleküle stark gestörte, knäuelartige Struktur.
Lithium based coordination catalysts for the hydrogenation of diene and vinylaromatic polymers
Authors: Falk John Carl 
Published: April 2003

AbstractA new method is described to hydrogenate polymeric unsaturation. The hydrogenation of polybutadiene, polyisoprene and polystyrene is effected with coordination catalysts derived from alkyl or aryl lithiums and transition metal salts of 2‐ethylhexanoic acid. The catalyst activity is discussed as a function of lithium‐transition metal ratio, catalyst concentration, temperature, and hydrogen pressure.
Photopolymerization of methyl methacrylate induced by trithiocyanatotripyridine iron(III) complex
Authors: Sakota Naokazu , Takahashi Kazunobu , Nishihara Koji 
Published: April 2003

AbstractThe photopolymerization of methyl methacrylate (MMA) in the presence of trithiocyanatotripyridine iron(III) complex (Fe(SCN)3Py3) was kinetically studied. The overall rate of photopolymerization (Rp) in ethanol at 35°C was shown as following:

The obtained value of kp/k was satisfactorily consistent with those reported for the radical polymerization of MMA hitherto. The overall activation energy of the polymerization was calculated to be 3.0 kcal/mole, and the value of Ep − 1/2 Et obtained from the log kp/k versus l/T curve was 3.1 kcal/mole.These kinetic data and the composition curve of the copolymerization of MMA and styrene showed that the photopolymerization with the iron(III) complex proceeded via a free radical mechanism and that the monomer participated in the initiation step.
Estimation of chemical inversions of monomer placement in polypropylene by pyrolysis gas chromatography
Authors: Seno Hiroshi , Tsuge Shin , Takeuchi Tsugio 
Published: April 2003

AbstractA unique method of estimating the amount of chemical inversions in monomer placement of isotactic and atactic polypropylene was developed by means of pyrolysis gas chromatography of its chlorination products. The molar proportion of mesitylene/pseudocumene was determined from the chromatograms of the pyrolysis products. The isomers of trimethylbenzene which are formed during the pyrolysis gave good information about the triads in the original polypropylene.
Sedimentation of dissolved macromolecules in the terrestrial gravitational field near the critical locus
Authors: Wolf B. A. 
Published: April 2003

AbstractThe present paper demonstrates theoretically as well as experimentally, that the gravitational field of the earth produces very pronounced changes in the equilibrium concentration of dissolved macromolecules with height, under near critical conditions.Thus it could be observed for the system polystyrene/cyclohexane that the equilibrium concentration at the bottom of a tube is approximately three times that at a height of 10 cm, under such conditions. In the case of polymolecular samples the sedimentation is associated with a corresponding fractionation.
Die spektroskopische untersuchung einer cyclischen, tetrameren verbindung aus p‐kresol und formaldehyd
Authors: Kämmerer Hermann , Happel Günter , Caesar Friedrich 
Published: April 2003

AbstractIn Anlehnung an den Syntheseweg von HAYES und HUNTER wurde eine cyclische, tetramere Verbindung (VII) über eine linear 4‐Kernverbindung (VI) (aus p‐Kresol und Formaldehyd) hergestellt. Ihre Struktur wurde spektroskopisch untersucht. Mittels UV‐ und IR‐Spektren läßt sich VII von der Ausgangsstufe VI und einem Konkurrenzprodukt VIII unterscheiden. Die H‐NMR‐Spektren der Ringverbindung und ihrer Ausgangsverbindung (VI) stimmen vollständig mit den angegebenen Strukturformeln überein; sie geben, bei 20 und 60°C aufgenommen, Hinweise auf bestimmte Konformere der Ringverbindung. Das massenspektrometrisch bestimmte Molekulargewicht (480) stimmt mit dem berechneten (480,6) überein.
Polymerization mechanism of N‐carboxy‐α‐amino acid anhydride by organometallic compounds. IV. Stereospecific association of diisobutylaluminum 4‐methyloxazolidonate as a model compound of intermediate of the polymerization
Authors: Makino Tetsuya , Inoue Shohei , Tsuruta Teiji 
Published: April 2003

AbstractIn the copolymerization of D‐ and L‐alanine N‐carboxy anhydride (NCA) with an excess of L‐antipode by triethylaluminum, a polyalanine containing an equal amount of L‐ and D‐residues was obtained in the early stage of the polymerization.Initiation of the polymerization was the hydrogen abstraction from NH group of the NCA by the trialkylaluminum.Since sarcosine NCA (N‐methylglycine NCA) was not polymerized with trialkylaluminum, alanine NCA is considered to be polymerized through the form of the metalated NCA. A stereochemical study on diisobutylaluminum 4‐methyloxazolidonate (BAO) as a model compound of the metalated NCA showed that BAO was associated with each other forming preferentially a meso‐dimeric structure. From this result, the metalated NCA is also considered to form preferentially a meso‐dimeric structure in conformity with the observed fact that the NCA polymerization produced in the early stage the polyalanine consisting of practically the same amount of L‐ and D‐residues.
Beitrag zur Auswertung der Molekulargewichtsverteilung von Polypropylen
Authors: Pechočová Marie , Pechoč Vladimír 
Published: April 2003

AbstractDurch Auswerten von Fraktionierdaten verschiedener Polypropylene und Polypropylenfasern wurde festgestellt, daß die untersuchten, handelsüblichen Polymeren eine logarithmische Normalverteilung der Molekulargewichte nach WESSLAU, die schwach abgebauten Polymeren eine korrigierte logarithmische Normalverteilung nach DAVIS, TOBIAS und PETERLI und die stark abgebauten Polymeren eine exponentielle Verteilung nach TUNG aufweisen.
Poly(1.4‐phenylen‐1.1‐diphenyläthylen) durch WURTZ‐synthese
Authors: Braun D. , Platzek U. 
Published: April 2003

AbstractDurch Reduktion von Diphenyl‐(4‐carboxy‐phenyl)‐methanol mit LiAlH4 gelangt man zum Diphenyl‐(4‐hydroxymethyl‐phenyl)‐methanol, das mit Thionylchlorid in Diphenyl‐(4‐chlormethyl‐phenyl)‐methylchlorid übergeführt wird. Die WURTZ‐Synthese mit Natrium in Toluol ergibt Poly(1.4‐phenylen‐1.1‐diphenyläthylen) mit einem Molekulargewicht Mn = 2030 (P̄n = 8). Der Polymerisationsgrad wird durch Bildung monofunktioneller Verbindungen wie Diphenyl‐(4‐chlormethyl‐phenyl)‐methan und durch die Spaltung der Polymerketten mit Natrium beeinflußt.
Photodegradation behavior of some vinyl ketone copolymers
Authors: Kato Masao , Yoneshige Yasuo 
Published: April 2003

AbstractPhotodegradation behavior for copolymers of styrene (St), α‐methyl styrene (α‐MSt) and methyl methacrylate (MMA) with methyl vinyl ketone (MVK) and phenyl vinyl ketone (PVK) in the presence of air was investigated in the solid state and in solution.Photolysis of St/MVK and St/PVK copolymers proceeded smoothly and an increase of the ketone in the copolymer resulted in an increase of the rate of degradation. Generally, the rate of degradation is faster in St/PVK copolymers than in St/MVK copolymers. It is likely that the degradation of the copolymers takes place mainly through NORRISH type II reaction.It was found that the photolysis of α‐MSt/PVK copolymers was retarded considerably as compared with St/PVK copolymers.An unexpected behavior was observed in the case of MMA/MVK or MMA/PVK copolymers. These copolymers were expected to degrade with slow rates; they degraded, however, rapidly. Some experiments were done to explain this phenomenon.
Heterophases in block‐copolymer/solvent systems in the liquid and in the solid state
Authors: Sadron Charles , Gallot Bernard 
Published: April 2003

AbstractA general review of the observed isothermal phase diagram (structure as a function of the concentration) of a number of (A–B)/S systems is given where A–B is a linear blockcopolymer containing the long sequences A and B and S is a preferential solvent for one of the sequences.Special attention is devoted to the third region of the diagram (large concentration of A–B) where periodic and regular (mesomorphic) structures are observed.The effect of the concentration on the structure (cubic, hexagonal and lamellar) and on the values of the structural parameters as they are observed by X‐ray diffraction or electron micrography is discussed.It is shown that the type of structure of a given A–B copolymer in a given solvent S is determined mainly by the ratio of the volumes of the phase containing the insoluble sequence and the volume of the phase formed by the solution, a fact which can be considered as a generalization of a law given by G. E. MOLAU.
Cyclopolymérisation du diméthacrylate de dihydroxy‐2,2′‐diméthyl‐5,5′‐diphénylméthane
Authors: Guéniffey Henri , Kämmerer Hermann , Pinazzi Christian 
Published: April 2003

AbstractLa cyclopolymérisation du diméthacrylate de dihydroxy‐2,2′‐diméthyl‐5,5′‐diphénylméthane (II) a été réalisée en milieu benzène à 80° avec l'azobisisobutyronitrile comme amorceur, en milieu toluène à −500°C avec le butyllithium comme amorceur et en tétrahydrofuranne (THF) avec le naphthalène sodium. Les polymères obtenus ont été soumis à l'hydrolyse basique, les polyacides résultants traités par le diazométhane donnent les polyméthacrylates de méthyle correspondants dont la tacticité a été étudiée en NMR (100 MHz). La réduction des polymè;res a été effectuées par LiAlH4 en milieu THF. Des alcools polyméthylallyliques ont été isolés. Les résultats semblent montrer l'influence de la matrice II sur le degré de tacticitt du polyrnéthacrylate de méthyle.
Solvent effects on stereoregularity of poly(vinyl trifluoroacetate) obtained by radical polymerization
Authors: Matsuzawa Shuji , Yamaura Kazuo , Noguchi Hiroji , Hayashi Hiromichi 
Published: April 2003

AbstractVinyl trifluoroacetate was polymerized by free radicals in various kinds of solvents at temperatures between +60 and ‐40°C. The syndiotactic and isotactic diad contents of the polymer were determined via the triad content, which was obtained by their NMR‐spectra.The differences of the activation enthalpies and those of the activation entropies between isotactic and syndiotactic arrangements were calculated from the temperature dependence of the ratio of isotactic to syndiotactic diads formed in the different solvents. A compensation effect exists between the two differences. The syndiotacticities of the polymers synthesized in alkanes in which the polymers were insoluble were higher than those in esters and ketones in which the polymers were soluble.The syndiotactic diad contents of the polymer synthesized in alkanes and ketones at −40°C amount to 60∼63% and 52∼56% respectively.