bluuebunny/crossref_metadata_2025_split huggingface dataset:
Über den Mechanismus der Entstehung von 1.3.5‐Trioxacycloheptan bei der kationischen Polymerisation von 1.3‐Dioxolan
Authors: Boehlke K. , Jaacks V. 
Published: April 2003

AbstractDie von MIKI, HIGASHIMURA und OKAMURA beschriebene Bildung von Trioxacycloheptan während der kationischen Polymerisation von Dioxolan wird durch Spuren von Wasser verursacht und ist nicht auf die von MIKI et al. postulierte backbiting‐Reaktion zurückzuführen. Wasser führt durch Polymerisationsübertragung zu Hemiformal‐Endgruppen, aus welchen Formaldehyd abgespalten wird, der dann zusammen mit Dioxolan Trioxacycloheptan ergibt. Die Trioxacycloheptankonzentration steigt schon nach kurzen Polymerisationszeiten nicht weiter an und ist direkt proportional der Menge an zugesetztem Wasser; dadurch ist eine bequeme und sehr empfindliche Bestimmung des Gesamtwassergehaltes im Polymerisationsansatz möglich.
Feldionen‐ und Elektronenstoß‐Massenspektrometrie von Polymeren und Copolymeren. I. Fortschritte in der Methodik der Pyro‐Feldionenmassenspektrometrie
Authors: Hummel D. O. , Düssel H. J. , Rübenacker K. , Schweren Th. 
Published: April 2003

AbstractEin Massenspektrometer (CH 4 Varian MAT) mit einer kombinierten Elektronenstoß‐Feldionisationsquelle wurde für die Untersuchung makromolekularer Systeme modifiziert. Eine in diesem Institut entwickelte Pyrolyseschubstange ermöglichte Pyrolysetemperaturen von maximal 1200°C. Bei der eigenen Herstellung von Emissionsanoden mit günstigeren geometrischen Verhältnissen für die Feldionenquelle wurden besseres Trennvermögen und erhöhte Empfindlichkeit des Massenspektrometers sowie größere Festigkeit des Emitterdrahtes erzielt. Außerdem wurde die Veränderung der Emitteroberfläche durch elektronenmikroskopische Untersuchungen aufgeklärt.
Synthesis of optically active poly(L‐α‐hydroxyisovalerate) and poly(L‐α‐hydroxyisocaproate)
Authors: Iwakura Yoshio , Iwata Kaoru , Matsuo Shunji , Tohara Akifumi 
Published: April 2003

AbstractOptically active poly(L‐α‐hydroxyisovalerate) and poly(L‐α‐hydroxyisocaproate) were prepared by the ring‐opening polymerization of the corresponding glycolides, and their physical properties were studied.The polymerization conditions to obtain polymers with high molecular weight and high optical purity were also examined.
Polymérisation du méthylènecyclobutane obtention de l'isocaoutchouc
Authors: Pinazzi Chr.P. , Brossas J. 
Published: April 2003

AbstractLa polymérisation cationique du méthylènecyclobutane (isomère de l'isoprène) donne un polymère à enchaînement principalement cyclobutanique. Avec des catalyseurs ZIEGLER‐NATTA, le polymère a la structure d'un polyisoprène partiellement cyclisé; en présence d'acetylacétonates de métaux de transition et de catalyseurs de ZIEGLER‐NATTA ternaire, l'isopolyisoprène est obtenu pratiquement pur. Ce polymère est un isomère du polyisoprène et possède ses doubles liaisons en position exo par rapport à la chaǐne.
Polymere Reagenzien. I. Einfluß der Porenstruktur bei Copolymeren aus Äthylvinylbenzol und Divinylbenzol auf die Halogenierung
Authors: Heitz Walter , Michels Rudolf 
Published: April 2003

AbstractPolymere Reagenzien sind meist vernetzte Polymere mit funktionellen Gruppen, mit denen auch bei Anwendung eines großen überschusses eine chemische Reaktion durchgeführt werden kann, ohne das Reaktionsmedium zu verunreinigen. Die Gesichtspunkte, die optimale Eigenschaften der Polymermatrix erwarten lassen, werden diskutiert.Eine Reihe von stark vernetzten Polyäthylvinylbenzolharzen wurde hergestellt und durch Bestimmung der inneren Oberfläche und der Porengrößenverteilung charakterisiert. Diese vernetzten Copolymeren werden jodiert und bromiert.
Der NMR‐spektroskopische Nachweis der m‐Substitution bei der Kondensation von chlormethylierten Nitrophenolen mit Methylphenolen
Authors: Böhmer Volker , Mathiasch Bernd 
Published: April 2003

AbstractDie Kondensation von drei chlormethylierten Nitrophenolen mit p‐Kresol und 2.4‐Dimethylphenol wurde untersucht. Mit Zinkchlorid als Katalysator und bei etwa 100°C entstehen stets zwei Hauptprodukte, die in allen Fällen getrennt und in rGeiner Form erhalten wurden. Hauptsächlich anhand ihrer NMR‐Spektren konnte gezeigt werden, daß es sich um die isomeren 2.2′‐Dihydroxy‐ bzw. 2.3′‐Dihydroxydiphenylmethanderivate handelt. Die Substitution erfolgt demnach nicht nur in ortho‐, sondern auch in meta‐Stellung zur phenolischen OH‐Gruppe. Das Verhältnis, in dem beide Produkte nebeneinander gebildet werden, konnte ebenfalls NMR‐spektroskopisch bestimmt werden. Der Anteil an 2.3′‐Dihydroxydiphenylmethanderivaten ist überraschend hoch und liegt im Bereich von 15 bis 55%.
Synthese und Polymerisation einiger 6‐substituierter 9‐Vinylpurine
Authors: Takemoto Kiichi , Kawakubo Fumio , Kondo Koichi 
Published: April 2003

Abstract6‐Methylamino‐, 6‐Di‐n‐propylamino‐ und 6‐Di‐n‐butylamino‐9‐vinylpurin wurden durch die Umsetzung der entsprechenden Alkyl‐ bzw. Dialkylamine mit 6‐Chlor‐9‐vinylpurin in wäßriger Lösung hergestellt. Die Polymerisation sowie die Copolymerisation dieser Verbindungen wurde untersucht. Alle erhaltenen polymeren 9‐Vinylpurine zeigten mit Ribonucleinsäure in wäßriger Lösung fast keinen hypochromen Effekt.
Syntheses and reactions of functional polymers. LX. Copolymerization of N‐vinyl‐pyrrolidone with methacrylic acid
Authors: Endo Takeshi , Numazawa Ryozo , Okawara Makoto 
Published: April 2003

AbstractThe copolymerization of N‐vinyl‐pyrrolidone (VP) with methacrylic acid (MA) was studied and the following results were obtained. (1) The molar ratio MVP/MMA in the copolymer is ca. 1. (2) The rate of polymerization reaches a maximum for a molar ratio of the monomers MVP/MMA = 1. (3) The rate increases in mixtures of dimethylformamide (DMF) and methylene chloride as the content of CH2Cl2 increases. (4) The rate and the ratio MVP/MMA in the copolymer decreases in mixtures of DMF and water as the amount of water in increased.
Physicochemical studies of oligodextran. II. Intrinsic viscosity‐molecular weight relationship
Authors: Gekko Kunihiko 
Published: April 2003

AbstractThe viscosity behavior of dextran in two good solvents and four mixtures of a good and a bad solvent was studied over the molecular weight range of 410 < Mn < 32,000 at 25 and 50°C. In the molecular weight region larger than 2,000, the plot of log [η] versus log Mn gave the usual linear relationship for all solvents used. The constants K and a of the equation [η] = KMa were determined and their dependence on the concentration of the nonsolvent in mixed solvents and on the temperature were discussed. Using the unperturbed dimensions of the dextran molecule estimated from the Stockmayer‐Fixman plots, the value of {〈L〉/〈L〉}1/2 was calculated to be 1.7–1.8. The viscosity behavior for dextran with Mn < 2,000 was qualitatively discussed as a deviation from the randomly coiled model.
Cyclocopolymerisation unter intramolekularer lactonringbildung
Authors: Sackmann Günter , Kolb Günter 
Published: April 2003

AbstractDie radikalische Copolymerisation von Maleinsäureanhydrid mit Allyl‐ und Methallylalkohol ergibt lineare und lösliche (1:1)‐Copolymere. Diese enthalten hauptsächlich Carboxylgruppen und Lactonringe. Es wird ein Reaktionsmechanismus für die Bildung solcher Cyclocopolymerer vorgeschlagen. Die Substitution eines Teils des Allyl‐ bzw. Methallylalkohols durch dritte copolymerisierbare Verbindungen führt zu Terpolymeren, die neben Lactonringen noch unveränderte cyclische Anhydridgruppen enthalten.
Etude de la polymérisation des derivés acétylèniques XIIIème note. synthèse et propriétés du polyphénylthioacétylène
Authors: Simionescu Cr. , Dumitrescu Sv. , Percec V. 
Published: April 2003

AbstractLe monomère phénylthioacétylène (FTA) synthétisé d′après les méthodes classiques a été polymérisé par mécanisme ionique, en présence de (C2H5)2O BF3 comme catalyseur. La polymérisation du FTA n'est pas connue dans la littérature. Le nouveau polymère obtenu a été étudié en ce qui concerne la structure et ses propriétés semiconductrices.
IR‐Studies of drawn polyethylene part III. The orientation of vinyl and methyl end‐groups
Authors: Glenz W. , Peterlin A. 
Published: April 2003

AbstractThe first increasing and soon saturating IR dichroism of several bands originating from methyl and vinyl end‐groups in cold drawn linear polyethylene has been related to the mean orientation of the end‐groups and the preceding CH2 sequences (cilia). Several possible conformations of the end‐groups with respect to the backbone chain are discussed. In the case of the methyl end‐groups the experimental data can be interpreted in two ways: (a) Assuming that the orientation results exclusively from methyl end‐groups which are incorporated in the crystal lattice, it follows that only 17–35% of these groups can be in the crystalline phase. (b) If all end‐groups are located in the amorphous phase one can derive an orientation function for the end‐groups and the cilia given as f = 0.4–0.8. The dichroism of bands resulting from the vinyl end‐groups cannot be interpreted unequivocally. The expected dichroism of a vinyl end‐group in its supposed most stable conformation is in qualitative disagreement with the experimental value. The conformation which is consistent with the observed dichroism and would lead to an orientation function f = 0.55 for the vinyl end‐groups and the cilia, does not represent a stable rotational isomer as discussed from the rotational potential of simple model compounds. Reasons for this discrepancy are discussed.
Der kristalline anteil des polyoxymethylens
Authors: Wilski Hans 
Published: April 2003

AbstractEs wurden die spezifischen Volumina verschiedener handelsüblicher Polyoxymethylen‐Sorten (Homopolymerisate Delrin® und Acetalcopolymerisate Hostaform®) sowie einer Reihe Trioxan/1.3‐Dioxolan‐Copolymerisate mit Dioxolan‐Gehalten von 6,3 bis 100% im Temperaturbereich −35°C bis +200°C dilatometrisch gemessen. Die thermisch sehr stabilen und z. T. sehr niedrig schmelzenden Copolymerisate erlaubten eine genaue Bestimmung der Temperaturabhängigkeiten der spezifischen Volumina der Schmelzen und damit eine genaue Bestimmung der spezifischen Volumina der amorphen Phasen auch bei 20°C. Die Neigungen der Schmelzgeraden ergaben sich unabhängig von der Zusammensetzung zu B = 5,78·10‐4 cm3/g°C, die spezifischen Volumina der amorphen Phasen bei 20°C für reines Polyoxymethylen zu 0,7553 cm3/g und für das Copolymerisat (Trioxan/2 Gew.‐% Äthylenoxid) zu 0,7578 cm3/g. Die hieraus berechneten kristallinen Anteile liegen für aus der Schmelze kristallisierte Proben bei 64–69 bzw. 56–59%, also rund 12% niedriger als bisher angenommen wurde. Es wird ein Dilatometer‐Ofen für genaue dilatometrische Messungen beschrieben.
Effects of branching on some properties of ethylene/α‐olefin copolymers
Authors: Shirayama Kenzo , Kita Shin‐Ichiro , Watabe Hiroshi 
Published: April 2003

AbstractCopolymers of ethylene with relatively small amount of nine species of α‐olefins, i.e., propylene, butene‐1, pentene‐1, hexene‐1, octene‐1, dodecene‐1, octadecene‐1, 4‐methylpentene‐1, and 4.6‐dimethylheptene‐1 were prepared with the use of ZIEGLER‐NATTA catalyst and their melt properties, crystalline behaviors, and various physical properties were investigated in relation to the side‐chain length and structure.The melt index‐intrinsic viscosity (MI‐[η]) correlation, melt tension, and melt extensibility were found to be hardly affected by the branches. On the crystalline behavior and physical properties, the effects of branching generally became more pronounced when the branch sizes became larger. It was noticeable, however, that ethyl and propyl branches exert strong effects in comparison with their relatively small sizes. It was also observed that the ethylene/octadecene‐1 copolymers have lower β‐peak heights and higher β‐peak temperatures in E″‐temperature curves than expected from their branch size, and this was considered to be due to the crystallization of the side‐chains. The properties of high pressure polyethylenes coincided, in many respects, with those of the copolymers having bulky branches.
Über die Strukturbildung aus Salzlösungen der ataktischen Polymethacrylsäure mit n‐Alkylaminen
Authors: Fakirov S. , Simov D. , Baldjieva R. , Michailov M. 
Published: April 2003

AbstractEs wird der Einfluß der Kettenlänge der n‐Alkylamine auf die morphologische Beschaffenheit und die innere Anordnung der übermolekularen Strukturen untersucht, die sich aus wäßrigen und n‐Butanollösungen ihrer Salze mit ataktischer Polymethacrylsäure bilden. Alle im Licht‐ und Elektronenmikroskop beobachteten Strukturen zeichnen sich durch eine vollkommene morphologische Beschaffenheit aus. Die Salze höherer n‐Alkylamine (C4, C6, C12 und C17) sind optisch anisotrop. Das n‐Butylaminsalz weist ein kristallines Elektronenbeugungsbild auf. Die Salze der höheren n‐Alkylamine schmelzen in einem engen Temperaturbereich. Auf Grund dieser Angaben wird vermutet, daß die beobachteten übermolekularen Strukturen der Salze von ataktischer Polymethacrylsäure mit niedrigen n‐Alkylaminen (bis C4) aus der Hauptpolymerkette gebildet werden. Die optisch anisotropen Strukturen mit kristallähnlichem innerem Bau der Salze höherer n‐Alkylamine (mehr als C4) sind dagegen auf die n‐aliphatische Seitenkette zurückzuführen.
Solvent effects on the alternating copolymerization systems. Evaluation on equilibrium constants by NMR spectroscopy
Authors: Tsuchida Eishun , Tomono Tsugikazu , Sano Hideo 
Published: April 2003

AbstractThe contributions of the charge‐transfer complexes to the alternating copolymerizations (e.g., the styrene/maleic anhydride system) were studied. From the facts that the complex concentrations changed in various solvents and the rates of copolymerization depended on the solvent species, the behavior of the alternating copolymerization was considered to be controlled by the quantities of the reactive monomer complexes.In relatively strong donor solvents such as acetone and tetrahydrofuran, the concentrations of the monomer complexes were low because acceptor monomers also form complexes with the solvents. Therefore, the contributions of the monomer complexes to the copolymerization were neglectable. On the other hand, in benzene and carbon tetrachloride, which interact with acceptor monomers relatively weakly, the concentrations of the monomer complexes were relatively high. Then the copolymerizations were mainly controlled by the reactive monomer complexes.After all, it was suggested that the uncomplexed monomers as well as the complexed monomers should be taken into account on discussing the mechanisms of the alternating copolymerization between donor and acceptor monomers. In addition, the equilibrium constants or the complex concentrations could be determined in n‐hexane by the use of NMR spectra.
Studies on the polymerization of bifunctional monomers. XXI. Polymerization of o‐diethinylbenzene
Authors: Aso Chuji , Kunitake Toyoki , Saiki Kenzaburo 
Published: April 2003

AbstractPolymerizations of o‐diethinylbenzene were conducted with ZIEGLER‐type and other catalysts. Polymers were readily obtained with

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as catalysts. Combinations of alkylaluminium compounds with other transition metal acetylacetonates were much less effective as catalysts. The polymers obtained with these catalysts are pale brown to brown powders with a mol. wt. of 2000 to 3500, which do not melt nor decompose up to 300°C. Small amounts of polymers were also obtained with cationic catalysts and with azobisisobutyronitrile as initiator.From NMR and IR spectroscopic data, the polymers obtained with coordination catalysts were shown to contain 30–50% of the unreacted second ethinyl group. The methyleneindene unit probably is involved as cyclic structure, although other structural units formed by head‐to‐head addition could not be excluded from the data available.
Addition reaction of multifunctional epoxides with silk fibroin
Authors: Shiozaki Hideki , Tanaka Yoshio 
Published: April 2003

AbstractThe reaction of di‐ and tri‐functional epoxides with silk fibroin was investigated in the presence of various salts in different solvents at 45–75°C. The reaction rates depend on the nature of the salts and the solvents used. Large weight gains (to 28%) were obtained in the reactions with ethyleneglycol diglycidyl ether, glycerol triglycidyl ether, and vinylcyclohexene dioxide catalyzed by thiosulfate, thiocyanate, cyanide, or chloride ions in such solvents as carbon tetrachloride, toluene, ethanol, and isopropanol. The weight gains in the silk/epoxide reaction were obtained mainly by the reaction of epoxide with the phenolic hydroxyl groups of the tyrosine residues, although lysine, histidine, arginine, and serine residues were found to react. The silk fabrics reacted with the epoxides were imparted with low solubilities in aqueous NaOH and HCl solutions without an appreciable decrease of moisture regain and flexibility of the fabric, and had much improved creaseproof properties.
Ring‐chain competition kinetics in linear polymers
Authors: Gordon M. , Temple W. B. 
Published: April 2003

AbstractRecent data of STEPTO and WAYWELL for ring‐chain competition in the kinetically controlled polymerizing system (i.e. backward rate = 0) of (polyethylene glycol)/(hexamethylene diisocyanate) have been fitted by exact computer calculations, assuming GAUSSian chain statistics. A good one‐parameter fit is obtained. The optimum value of the parameter is compared with theory. The results suggest that the solvent used (benzene at 70°C) is thermodynamically poor for this polymer system.
Effect of structural variations on the thermo‐oxidative stability of aromatic polyimides
Authors: Dine‐Hart R. A. , Wright W. W. 
Published: April 2003

AbstractPolyimides were synthesised from a number of diamines and dianhydrides and their stability determined by thermogravimetric analysis at 400°C in air. Wherever possible high molecular weight films obtained by thermal condensation of the polyamic acid intermediates were studied. If this was not possible, films obtained from acetic acid anhydride ciclised polymers or thermally cured powders were used.A well defiend order of stability was observed for the polyimides prepared from pyromellitic dianhydride and a variety of diamines. The simplest and most symmetrical structures had the greatest thermal stability. Lowest stabilities were observed when linking groups were electronegative in nature.
Crystallization of polypeptides in the course of polymerization. I. Growth mechanism of poly‐L‐ and DL‐alanine crystals
Authors: Kōmoto Tadashi , Akaishi Tadashi , Ōya Masanao , Kawai Tōru 
Published: April 2003

AbstractIn order to pursue the possibility of the extended chain crystals formed in the course of polymerization, kinetics of the heterogeneous polymerization of L‐ and DL‐alanine NCA in acetonitrile and the morphologies of the resultant polymers were studied. Electron microscopy revealed that the fibers formed in the beginning of polymerization thickened as the polymerization proceeded and that the growth mechanism of the polypeptide crystals is quite similar to that of polyoxymethylene crystals during the polymerization of trioxane in cyclohexane. The X‐ray diffraction patterns and IR spectroscopy revealed that the growing chain molecules, when they attained a certain degree of polymerization (DP = ca. 3–4) beyond which they lost the solubility in the system, crystallized into the form of ribbon‐like fibers in which molecules, with the β conformation, were aligned perpendicularly to the fiber axis. As the growing chains attained a critical length by further polymerization, they began to take the α‐helical conformation which seemed to be more stable than the β conformation in the later stages. Thereafter, the crystals grew successively, taking the α‐helical conformation, through addition of the monomer molecules onto the reactive chain ends.The grown polypeptide chains were rather loosely packed but extended α‐helices in the crystals throughout the polymerization. Possible mechanisms are proposed for the nucleation and the subsequent growth of the crystals in the course of polymerization.
Vinyl polymerization. 277. Polymerization of vinyl pyridines in the presence of poly(maleic anhydride)
Authors: Shima Kazuhiro , Kakui Yasuhiko , Kinoshita Masayoshi , Imoto Minoru 
Published: April 2003

Abstract4‐ and 2‐Vinyl pyridine and N.N‐dimethylaminostyrene polymerize spontaneously at 50°C in the presence of poly(maleic anhydride) (PMAN). The polymer yields are quantitative and the obtained polymers consist of 1 : 1 mixture of poly(vinyl pyridine) (poly(VP)) and PMAN. Poly(VP) (P = 14) was separated from the mixture of poly(VP) and PMAN (P = 12), by means of solvent extraction and purification with ion exchange resin. The polymerization was considered to proceed through a mechanism of matrix polymerization. The adsorption or concentration of donor monomers on acceptor polymer may be caused by a charge transfer interaction.
Synthesis of poly(vinyl alcohol) with pending N‐derivatives of nucleic acid bases
Authors: Seita Toru , Yamauchi Kiyoshi , Kinoshita Masayoshi , Imoto Minoru 
Published: April 2003

AbstractN‐coupled (2‐dihydrogenphosphato)‐ethyl derivatives of nucleic acid bases and its analogues were synthesized and grafted onto poly(vinyl alcohol) using N.N′‐dicyclohexylcarbodiimide as a dehydrating agent in refluxing dimethylformamide/water (9:1). (2‐Dihydrogenphosphato)‐ethyl derivatives of adenine, theophylline, hypoxanthine, and thymine were incorporated up to 12, 75, 52, and 68% with respect to the amount of hydroxy groups of poly(vinyl alcohol), respectively. White water‐soluble products were obtained. Mixtures of poly(vinyl alcohol) having nucleicacid bases as side group and denatured yeast RNA or sperm DNA showed hypochromicity up to 16% in 0.1 M Na2HPO4 solution.
Dehydrohalogenation of polyvinylchloride in tetrahydrofuran solution with alcoholic KOH
Authors: Shindo Yohji , Hirai Toshikazu 
Published: April 2003

AbstractA dehydrohalogenation reaction between THF solution of PVC and alcoholic KOH has been studied in the temperature range from 18 to −12°C using UV and visible spectroscopy. The absorption spectra of dehydrohalogenated PVC consist of a series of absorption maxima between 260 and 450 mμ due to the formation of conjugated polyene sequences. The presence of oxygen has no effect on the dehydrohalogenation. The kinetics and mechanism of this reaction are discussed and the over‐all activation energy is determined. The proposed mechanism is an ionic elimination reaction similar to the dehydrohalogenation of alkylhalide with a basic reagent in solution. The preferable conditions for this reaction are proposed. It is also suggested that the conjugated polyene sequences are distributed rather selectively among the polymer chain.
The mechanism of polymerization and the solvent effect in the formation of polycation polymers of integral type
Authors: Tsuchida Eishun , Sanada Kei , Moribe Kazuhiko 
Published: April 2003

AbstractThe reaction of p‐xylylene dichloride (XDC) and N.N.N′.N′‐tetramethylethylenediamine (TED) in several solvents proceeds by nucleophilic bimolecular substitution (SN2), just as in a normal MENSCHUTKIN reaction, to form a polycation polymer of the integral type. However, the rate of the reaction decreases as the polymerization proceeds. This may be attributed to the decrease in the functional concentrations and, especially to the rapid decrease in the rate constant, for the reactivities of the end functional groups, i.e., the nucleophilicity of the end amino groups becomes much lower than the nucleophilicity of the monomers because of the inductive effect of the charge sites formed during the propagation. The influence of the solvent is measured and discussed.