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  • 1
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cis (CP) and trans (TP) isomers of 1,3-pentadiene (piperylene) were homo and copolymerized with acrylonitrile (A) in bulk and emulsion, at 50°C, using azobisisobutyronitrile and potassium persulfate as free radical initiators. The cis isomer reacts more rapidly than the trans monomer. The copolymer compositions were determined from nitrogen analysis, 100-MHz 1H-NMR and 25-MHz 13C-NMR spectra. The results thus obtained show that both the bulk and emulsion processes yield copolymers characterized by a very similar composition. Data plotted according to the Kelen-Tüdös method indicate that the terminal-unit model is applicable to the piperylene-acrylonitrile system. Reactivity ratios for bulk copolymerization were as follows: rA = 0.079, rTP = 0.114, and rA = 0.033, rCP = 0.188. These values are very small and hence suggest a strong alternating tendency for acrylonitrile and 1,3-pentadiene in both comonomer systems. This latter conclusion is corroborated by the comparison of the NMR spectra of the synthesized copolymers with that of a standard alternating sample. The reactivity (Q) and electronegativity (e) of the 1,3-pentadiene isomers calculated from the reactivity ratios by the Alfrey - Price equations were QTP = 0.56, eTP = -0.97 and QCP = 1.215, eCP = -1.055 for trans and cis dienes, respectively.
    Additional Material: 8 Ill.
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  • 2
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The microstructure of diene units was investigated in radical homopolymers of the cis and trans isomers of 1,3-pentadiene and copolymers with acrylonitrile, synthetized in bulk and emulsion. Experiments were carried out by infrared spectroscopy, 100 MHz 1H-NMR, and 25 MHz 13C-NMR studies. No difference between the bulk and emulsion samples was noted. The microstructure of poly(1,3-pentadiene) is practically independent of the cis or trans configuration of the diene monomer and is as follows: 56-59% trans-1,4, 15-17% cis-1,4, 16-20% trans-1,2 7-10% cis-1,2 and 0% 3,4. On the other hand, up to about 30% of incorporated acrylonitrile (10% in the feed), the microstructure of the pentadiene fraction in the copolymers is not affected. This finding suggests that the penultimate unit has very little influence on the polymerization process involving the terminal pentadienly unit. Beyond 10% of acrylonitrile in the feed, the proportions of the structural units were linearly dependent upon the acrylonitrile content: trans-1,4 content increased whereas the amounts of cis-1,4 trans-1,2 and cis-1,2 decreased (except the cis-1,2 fraction, constant in the copolymers from the cis-diene). These results are discussed on the assumption that the microstructure of pentadiene residues is strongly associated with the acrylonitrile comonomer in the feed.
    Additional Material: 9 Ill.
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  • 3
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Anionenaustauscheigenschaften von Polyurethanfilmen wurden als Funktion ihres Stickstoffgehalts untersucht. Quellungs-, Wasserdampfdurchlässigkeits-, Anionenaustauscherkapazitäts-, spezifische Ionenleitungswiderstands- und Permselektivitätsmessungen zeigen, daß sich diese Filme tatsächlich wie Membranen mit durchschnittlichen Eigenschaften verhalten. Hinsichtlich der stöchiometrischen Zusammensetzung aus beiden Komponenten bringt die Herabsetzung des Stickstoffgehaltes eine Verminderung der Korrosionsschutzeigenschaften des Filmes. Andererseits müßte der Stickstoffgehalt erheblich erhöht werden, um die Schutzeigenschaften merklich zu verbessern. Eine solche Erhöhung ginge jedoch zu Lasten der mechanischen Eigenschaften des Anstrichs.
    Notes: Les propriétés de membranes échangeuses d'anions de films de résines de polyuréthannes ont été examinées, en fonction de leur teneur en azote. Les mesures de gonflement, de perméabilité à la vapeur d'eau, de capacité d'échange d'anions, de résistivité ionique transversale et de permsélectivité montrent que ces pellicules peuvent ětre effectivement considérées comme de médiocres membranes. Par rapport à la composition correspondant à la stoechiométrie des deux réactifs, un abaissement de la teneur en azote conduit à un affaiblissement des qualités de protection anti-corrosion; en revanche, il faudrait une élévation considérable de cette teneur pour améliorer sensiblement ces qualités, au détriment des propriétés mécaniques du revětement.
    Additional Material: 9 Ill.
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  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four oligomers of α-L-glutamic acid with ends blocked by nonionizable protecting groups were studied in 0.1M NaClO4 solution using potentiometric measurements. The titrations were analyzed using a pit-mapping method. The results are compared with those obtained with the corresponding polymer. The successive dissociation constants of the carboxylic side chains are obtained for oligomers with degrees of polymerization varying from 1 to 6. Then the successive stability constants corresponding to the association Cu2+-oligomer are given, and the MpHqLr distribution is calculated for each oligomer introducing MHqL complexes.
    Additional Material: 6 Ill.
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  • 5
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper investigates the possibility of using the method of flash pyrolysis-gas chromatography for the quantitative determination of the composition of free-radically prepared cis- or trans-1,3-pentadiene-acrylonitrile copolymers and for evaluation of their comonomer sequence distributions in terms of the run numbers. The experiments (sample weight: 50 μg, pyrolysis time: 4 s) were carried out, under a flow of helium, at a thermolysis temperature ranging from 450 to 900°C with a Curie-point pyrolyzer. After discussion of the respective thermal behaviors of the poly(1,3-pentadiene), polyacrylonitrile, mixtures of these homopolymers, and various kinds of copolymers (radically or fully alternating samples), the pyrolysis-gas chromatographic characterization of the primary structure of copolymers was studied, between 500 and 800°C, through the quantitative treatment of the corresponding liberated monomers which appeared on the pyrograms. By applying the both-side boundary effect theory on the molar amounts of these degradation products, which depend both upon copolymer composition and triad sequence distributions in the chain, the relative values of the monomer formation probability constants were calculated. The composition and the run number of each pyrolyzed sample were then determined using these parameters. The analytical data obtained by means of the procedure suggested are in very good agreement with those predicted, from reactivity ratios, by the usual theory of copolymerization (terminal-unit model) and with the evaluations provided by the 13C-NMR spectroscopy.
    Additional Material: 9 Ill.
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  • 6
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Highly active Ziegler-Natta catalysts have been synthesized using an electrochemical process in their preparation, with the aim of producing selectively titanium(III) species from TiCl4. The use of an undivided cell, an aluminium anode and a halogenated solvent (dichloromethane or 1,2-dichloroethane), has allowed the production in situ of chloroalkyl aluminium species, by cathodic reduction of TiCl4, thus giving rise to a new Ziegler-Natta catalytic combination. The possibility of scale up for this lectrochemical synthesis has been clearly shown. The Ti/Al system was modified so as to enhance its activity, first by adding a soluble dialkylmagnesium compound and then a soluble vanadium compound such as VOCl3. This Ti/Al/Mg/V highly active system was used under different conditions: in a hydrocarbon medium at low (80°C) and high (200°C) temperature and also under supercritical conditions in a continuous high-pressure autoclave reactor, to produce homoor copolymers of ethylene with α-olefins. Compared to similar heterogeneous catalysts obtained by comilling, the observed activities are shown to be very much improved, especially under high pressure and high temperature conditions. This may be related to the very narrow granular distribution centered at 2,5-3 μm, compared to a much broader distribution (centered at 6 μm) obtained with the comilled catalyst.
    Additional Material: 14 Ill.
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  • 7
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Iodine complexes of six monosubstituted polyacetylenes with methyl, ethyl, propyl, pentyl, t-butyl, and phenyl substituents have been characterized by electronic spectroscopy. UV spectra allow the determination of the nature and the amount of active species, and photoelectronic spectra confirm the nature of these species. These measurements indicate the presence of iodine in the I3- and I2 forms. The concentration of I3- is low (0.12-4.0 mol%), and it depends on the nature of the substitutent, but this amount does not decrease when the films are left under vacuum. On the other hand, the adsorption of ε high concentration of iodine is possible; this adsorption is governed by a diffusion mechanism and is reversible. Iodine doping leads to a cis-to-trans isomerization of the polymers, except for poly(3-3-dimethyl-1-butyne), which can be isomerized to the cis or to the trans form, depending on the solvent employed. Electrical properties of polymer I3- complexes are also reported. Conductivities of about 10-4 Ω-1 cm-1 are obtained for all polymers in the presence of an excess of iodine.
    Additional Material: 5 Ill.
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  • 8
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Um den Einfluß der Länge einer Vernetzerkomponente auf die Ionenaustauscheigenschaften von Acrylharzen zu studieren, wurden Acrylsäure-Methylacrylat-Diacrylat-Terpolymerisate synthetisiert. Bei diesen Terpolymerisaten sind Austauschkapazität und Vernetzungsgrad annähernd konstant, nur die Länge der Vernetzerkomponente ist verschieden. Die verwendeten Vernetzerkomponenten, deren Synthese verbessert wurde, sind Diacrylate linearer aliphatischer C2—C6-ω-Diole, von 1,4-Cyclohexandiol, von Hydrochinon und von Diäthylenglykol. Eine spezifische Polymerisationsmethode, die sich auf das kinetische Verhalten der Monomeren gründet, wurde entwickelt.
    Notes: Pour étudier l'influence de la longueur d'un agent de réticulation sur les propriétés d'échange d'ions de résines acryliques, on a été conduit à effectuer la synthèse de terpolymères d'acide acrylique, d'acrylate de méthyle et d'un diacrylate. Ces terpolymères ont une capacité d'échange et un degré de réticulation sensiblement constants; seule la longueur de l'agent de réticulation varie. Les réticulants utilisés, dont on a amélioré le mode de préparation, sont des diacrylates d' ω-diols aliphatiques linéaires de C2 à C6, du cyclohexanediol-1,4, de l'hydroquinone et du diéthylène-glycol. Une méthode spécifique de terpolymérisation, basée sur le comportement cinétique des monomères, a été mise au point.
    Additional Material: 4 Tab.
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  • 9
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zur Untersuchung der Bindungsart zwischen dem Hydratationswasser und dem makromolekularen Netzwerk wurden Polyurethanfilme unterschiedlichen Stickstoffgehalts der Wirkung eines Mikrowellenfeldes (10 GHz) ausgesetzt, dessen verschiedene Leistungsniveaus dazu dienten, Veränderungen in den dielektrischen Verlusten unter diesen Bedingungen zu verfolgen. Erhitzung und Entwässerung des polymeren Materials treten gleichzeitig ein, und die Geschwindigkeiten beider Prozesse stehen in engem Zusammenhang mit der chemischen Struktur des Makromoleküls.Die Ergebnisse lassen erkennen, daß im Verhältnis zur stöchiometrischen Zusammensetzung des Polyurethanharzes aus seinen beiden Komponenten das Wasser offenbar weniger stark an das Makromolekül gebunden ist, wenn dieses einen geringeren Stickstoffgehalt aufweist sowie Hydroxylgruppen enthält.Im Gegensatz dazu ist bei einer Zunahme des Gehalts an Urethangruppen über einen kritischen Wert hinaus eine stärkere Bindung des Wassers an das Netzwerk zu beobachten, was zur Folge hat, daß dem System zur Entwässerung eine höhere Leistung zugeführt werden muß.
    Notes: En vue d'examiner le mode de liaison entre l'eau d'hydratation et le réseau macromoléculaire, des films de vernis de polyuréthannes de différentes teneurs en azote sont soumis à l'action d'un champ électromagnétique de très haute fréquence (10 GHz), à différents niveaux de puissance, et l'on suit l'évolution des pertes diélectriques dans ces conditions. Le matériau s'échauffe et se déshydrate simultanément, et les vitesses d'échauffement et de déshydratation sont influencées par la structure chimique de la macromolécule. Il apparaît que, par rapport à la composition correspondant à la stoechiométrie des deux réactifs constituant le vernis de polyuréthannes, l'eau est moins fortement liée à la macromolécule quand celle-ci est de plus faible teneur en azote, et contient des groupes hydroxyles. Au contraire, quand la teneur en fonctions uréthannes croît au-delà de la teneur critique, l'eau est plus fortement liée au réseau, et l'on doit appliquer une puissance plus élevée au système pour obtenir sa déshydratation.
    Additional Material: 5 Ill.
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  • 10
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das mitlere Molekulargewicht von Chlorkautschuk ändert sich bei einer UV-Bestrahlung unterhalb 290-300 nm andersartig als oberhalb dieses Wellenlängenbereichs. Nach anfänglicher Abnahme um 25-30% steigt M̄n wieder auf die Höhe des Anfangswertes und fällt dann wieder ab. Es werden zwei mögliche Mechanismen für diese Molekulargewichtsänderung vorgeschlagen.
    Notes: Le raynonnement U. V. de longueur d'onde inférieure á 290-300 nm provoque une évolution de la masse moléculaire moyenne en nombre du caoutchouc chloré différente de celle de la lumière de λ〉290-300nm. On observe, après une décroissance de M̄n de l'ordre de 25-30%, une augmentation de celle-ci qui atteint sa valeur initiale pour décroitre après. Deux mécanismes possibles sont proposés.
    Additional Material: 2 Ill.
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