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  • 1
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 3-Methyl-2-isopropenyl-2-oxazolinium salts (4a, b) were prepared by alkylation of 2-isopropenyl-2-oxazoline (2). Their preparation is much easier than that of their vinyl analogues, 3-methyl-2-vinyl-2-oxazolinium salts, which cannot be isolated due to their high tendency to polymerization. 4a, however, was found, to show a low tendency toward radical and anionic polymerization, but it can be smoothly radically copolymerized with some vinyl monomers. The copolymerization parameters of 4a were determined and discussed in comparison with those of 2.
    Additional Material: 3 Ill.
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photoresponsive groups (azobenzene and cinnamic acid derivatives) were incorporated into alternating copolymers of maleic anhydride and vinyl ethers with pendant 4′-methoxy-4-biphenylyl moieties bound via ethylene glycol spacers. The resulting polymers were examined with respect to their liquid crystalline behavior and photochemical reactivity in relation to the isothermal phase transition behavior.
    Additional Material: 2 Ill.
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mesophase (lyotropic liquid crystal) of the inorganic rod-like polymer, imogolite, displays a typical fingerprint texture under a polarized optical microscope (POM), although the mesophase reveals no circular dichroism. The scanning electron microscope revealed a honeycomb structure of thin sheets having pleats in the freeze-dried sample prepared from the mesophase solution, and POM shows also a fingerprint texture from the same sample. A novel polarized optical microscopic observation procedure was introduced to eliminate the contrast variation and extinction due to the zero amplitude effect which depends on the orientational variation of anisotropic bodies with respect to a polarizer direction under the crossed Nicols. Various textures of lyotropic imogolite liquid crystals were observed with the procedure, and the results were accounted for by a honey-comb structure of curled thin sheats having pleats. The honey-comb model is consistent with the observation by scanning electron microscopy on the freeze-dried sample.
    Additional Material: 17 Ill.
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  • 4
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zwei Blockpolymerpräparate aus Styrol und Methylmethacrylat wurden nach dem von BAMFORD und JENKINS mitgeteilten Verfahren hergestellt. Die Herstellung, Isolierung und Charakterisierung dieser Blockpolymeren des ABA-Type werden als Ergänzung einer vorhergegangenen Kurzmitteilung7 beschrieben. Ferner beschäftigt sich die Arbeit mit den STAUDINGER-Indices, die in Diäthylmalonat und n-Butylchlorid erhalten wurden. Das Ergebnis legt die Vermutung nahe, daß die Molekülkonformation in diesen Lösungsmitteln durch eine gewöhnliche Knäelform, die sich von der in Toluol angenommenen unterscheidet, dargestellt wird.
    Notes: Two block copolymer samples of styrene and methyl methacrylate were prepared by employing the procedure described by BAMFORD and JENKINS. The preparation, isolation, and characterization of these A-B-A type block copolymers are reported in detail7. This paper further deals with the intrinsic viscosity data obtained in diethyl malonate and n-butyl chloride. The molecular conformation in these solvents is most likely to be of a random coil type differing from what the polymer chain would assume in toluene.
    Additional Material: 4 Ill.
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  • 5
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Konformation und molekulare Wechselwirkung der Modellverbindung eines Polyelektrolyten (2,4-Dimethylglutarsäure) in Alkohol/Wasser-Gemischen wurden mittels hochauflösender Kernresonanz untersucht.Es wurde gezeigt, daß sich die lokale Konformation der mesomeren 2,4-Dimethylglutarsäure in Alkohol/Wasser-Gemischen mit dem Molenbruch des Äthanols leicht ändert. Der Unterschied der chemischen Verschiebungen der beiden Methylenprotonen und die Verschiebung der Carboxylprotonen sind in vergleichbarem Maße vom Molenbruch des Äthanols abhängig. Diese Ergebnisse lassen jedoch nicht den Schluß zu, daß die Viskositätsänderungen von Polyacrylsäure oder Polymethacrylsäure in Alkohol/Wasser-Gemischen auf die durch die NMR-Daten belegten Änderungen lokaler Konformationen zurückzuführen sind. Tatsächlich dürfte der Gang der Viskositätskurve hauptsächlich auf die weitreichende Ketten-Wechselwirkung nicht benachbarter Segmente zurückzuführen sein.Es konnte gleichzeitig gezeigt werden, daß die lokale Konformation der mesomeren 2,4-Dimethylglutarsäure vom Lösungsmittel abhängt. Dies legt den Schluyz nahe, daß sich die lokale Konformation mit dem Lösungsmittel ändert.
    Notes: The conformation and molecular interaction of polyelectrolyte model compound (2,4-dimethylglutaric acid) in alcohol/water mixtures were investigated by using high resolution NMR spectroscopy.It is shown that the local conformation of meso-isomer in alcohol/water mixtures slightly changes with the mole fraction of ethanol. The difference in the chemical shifts of two methylene protons and the chemical shift of carboxyl protons are comparably dependent of the mole fraction of ethanol. These results, however, do not always mean that the change in the viscosity of poly(acrylic acid) or poly(methacrylic acid) in alcohol/water mixtures is due to the change of such local conformation as estimated by NMR. On the contrary, it is probably true that such change in the viscosity curve is mainly due to the long-range interaction between non-adjacent segments.It is also shown that the local conformation of meso-isomer depends upon the use of the solvents, leading to the conclusion that its local conformation varies with the solvent.
    Additional Material: 3 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The microstructure of poly(methyl methacrylate), (PMMA), prepared from methyl methacrylate with butylmagnesium chloride in toluene at -50°C in the absence (blank polymerisation) and presence of preformed isotactic PMMA (replica polymerization), was studied.In the blank polymerization, a relation was found between the microstructure of whole polymerization products and the conversion of monomer : the products obtained at lower conversions ( 〈10%) were predominantly isotactic, and the isotacticity decreased with increasing conversion, approaching a constant value. Furthermore the acetone-insoluble fractions of the products were separated into components on a preparative scale by a competitive adsorption method. The triad isotacticity of isotactic components was remarkably high (ca. 85%), while the triad syndiotacticity of syndiotactic components was ca. 60-70%. The molecular weight of the syndiotactic components was considerably lower than that of the isotactic components. On the other hand, the acetone-soluble fractions were assigned to be “atactic” from their behavior in thin layer chromatography.The polymerization products obtained by the replica polymerization, in sharp contrast with the products obtained by the blank polymerization, were predominantly syndiotactic, especially, when the mass ratio of produced polymer to added polymer was lower than ca. two. The difference between the two rates of polymerisation was within the experimental error.
    Notes: Gegenstand unserer Untersuchungen war die Konfiguration von Polymethylmethacrylat (PMMA), das aus Methylmethacrylat mit Butylmagnesiumchlorid in Toluol bei -50°C einmal in Abwesenheit (Blank-Polymerisation) und einmal in Gegenwart von vorgelegtem isotaktischem PMMA (Replica-Polymerisation) dargestellt wurde.Es zeigte sich, daß bei der Blank-Polymerisation eine Beziehung besteht zwischen dem Monomer-Umsatz und der Konfiguration der erhaltenen Polymerisate: die bei niedrigen Umsätzen (〈10%) erhaltenen Polymerisate waren hauptsächlich isotaktisch und mit zunehmendem Umsatz nahm die Isotaktizität zunächst ab, und nahm dann einen konstanten Wert an. Ferner wurden die acetonunlöslichen Fraktionen der Produkte mittels einer konkurrierenden Adsorptionsmethode in präparativem Maßstab in ihre Komponenten aufgetrennt. Der Anteil isotaktischer Triaden in der isotaktischen Kompo+nte war bemerkenswert hoch (etwa 85%), während der Anteil syndiotaktischer Triaden in der syndiotaktischen Komponente etwa 60 bis 70% betrug. Das Molekulargewicht der syndiotaktischen Komponente war beträchtlich niedriger als dasjenige der isotakti+hen Komponente. Aus dem Verhalten der acetonlöslichen Fraktionen bei der Dünn+hicht-Chromatographie ging hervor, daß sie ataktisch waren.Die Polymerisate, die bei der Replica-Polymerisation erhalten wurden, sind in scharfem Gegensatz zu den durch Blank-Polymerisation gewonnenen Produkten besonders dann +berwiegend syndiotaktisch, wenn das Mengenverhältnis von entstandenem zu zugegebe+em Polymeren niedriger als etwa zwei ist. Der Unterschied zwischen den beiden Polymerisationsgeschwindigkeiten liegt innerhalb der experimentellen Fehlergrenze.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Radical homopolymerization and copolymerizations of a new ionic monomer, 3-methyl-2-vinyl-5,6-dihydro-4H-1,3-oxazinium trifluoromethanesulfonate (2c), were studied. The homopolymerization was initiated with 2,2′-azoisobutyronitrile or benzoyl peroxide in acetonitrile to produce a polymer, poly[1-(3-methyl-5,6-dihydro-4H-1,3-oxazinium-2-yl)ethylene] (3c), with a relatively low solution viscosity ([η] ≈ 0,2). The monomer was found to be copolymerizable with both electron-rich (styrene and butyl vinyl ether) and electron-deficient monomers [methyl methacrylate (MMA)]. For the copolymerization of the monomer and MMA the reactivity ratios r1 = 0,31 and r2 = 0,37 (MMA) were determined. From these values the Q and e values were calculated to be 3,7 and 1,9, respectively. The e-value is one of the highest among vinyl monomers reported thus far, which is consistent with the anionic polymerizability of monomer 2c.
    Additional Material: 4 Tab.
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  • 8
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Argininosuccinate synthetase (EC 6.3.4.5) was immobilized on CNBr-activated Sepharose 4B. Properties of the immobilized enzyme are described and compared with those of the native enzyme. The immobilized enzyme was much more stable than the native enzyme at 37°C. It was further stabilized in the presence of the assay reagents. The optimum pH of the immobilized enzyme shifted towards alkalinity (approximately 0.5 unit). The apparent Michaelis constants measured for the immobilized enzyme were not greatly different from those measured for the native enzyme.Urea formation from citrulline was confirmed in a continuous column reactor by the coimmobilized argininosuccinate synthetase, argininosuccinate lyase (EC 4.3.2.1), and arginase (EC 3.5.3.1).
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Carbamoylphosphate synthetase (EC 2.7.2.5) and ornithine carbamoyl-transferase (EC 2.1.3.3) extracted from frog liver were successfully immobilized on CNBr-activated Sepharose 4B. The immobilized preparation had a better stability towards heat. The apparent Michaelis constant values for N-acetyl-glutamate, ammonia, and ATP were not significantly changed by immobilization.
    Additional Material: 7 Ill.
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  • 10
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The reactions of covalently immobilized heparin, abbreviated as I-Hep, with thrombin or Factor Xa were investigated both in the presence and absence of antithrombin III, AT III. Although I-Hep was able to bind to thrombin, the complex formation of thrombin and I-Hep did not affect the thrombin activity when measured by using a small artificial substrate, a peptide-MCA. Similarly, Factor Xa bound to I-Hep, but the activity of Factor Xa was not decreased in the absence of AT III, when a peptide-MCA was used for Factor Xa assay. Thrombin bound to I-Hep in much larger amounts than Factor Xa. Thrombin and Factor Xa were instantaneously inhibited by AT III in the presence of soluble heparin. However, when I-Hep was used instead of soluble heparin, instantaneous inhibition was not observed. When a natural, high-molecular-weight substrate was used for assay, the results were dependent on the structure of the immobilization carrier. Heparin immobilized on Sepharose 4B or Poly HEMA showed considerable prolongation of plasma recalcification time. However, heparin immobilized on the surface of PVA fiber did not prolong plasma recalcification time.
    Additional Material: 2 Ill.
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