bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthèse de copolymères séquencés par réaction entre des polymères ω‐et α,ω‐hydroxylés et des polymères ω‐et α,ω‐oxychloroformylés
Authors: Pinazzi Christian , Esnault Jacques , Pleurdeau Alain 
Published: April 2003

AbstractLa présente étude a pour but la réalisation de copolymères séquencés. Ces derniers sont synthétisés par réaction de condensation entre des homopolymères α‐ ou α,ω‐hydroxylés de motif monomère A et des homopolymères α‐ ou α,ω‐oxychloroformylés de motif monomère B. Les polymères utilisés dans cette étude sont des polyisoprènes, polybutadiènes α‐ ou α,ω‐hydroxylés et des polystyrènes α‐ ou α,ω‐oxychloroformylés. Les séquences des copolymères sont liées entre elles par des liaisons du type carbonate résultant de la réaction des fonctions terminales hydroxyle et oxychloroformyle. La structure de ces copolymères est confirmée par spectroscopie de NMR et IR et par des measures de masses moléculaires moyenne en nombre.
Teilchenbildung und abbruchsreaktion bei der fällungspolymerisation von styrol in methanol
Authors: Hoffmann Martin 
Published: April 2003

AbstractZu Beginn und in Gegenwart von nur wenig gefälltem Polymerem entspricht die Kinetik der Fällungspolymerisation von Styrol derjenigen von Lösungspolymerisationen, wobei jedoch das Verhältnis von Abbruchs‐ und Wachstumskonstante bei Molekulargewichten oberhalb 5000 erheblich größer als bei Lösungspolymerisationen ist.Bei Umsätzen unterhald 0,05% stellt sich eine während der weiteren Polymerisation konstante Teilchenzahl N ein. Bei konstanter Monomerkonzentration steigt N mit dem Quadrat des Molekulargewichtes, sinkt also mit wachsender Initiatorkonzentration ab. Die Theorie der Teilchenbildung muß deshalb neu überdacht werden.Gefälltes Polymeres vergrößert die Polymerisationsgeschwindigkeit proportional zu seiner Oberfläche, ohne die Polymerisation in der Lösung zu verändern. Nur ein kleiner Teil der entstehenden Polymerradikale lagert sich vor dem Abbruch des Wachstums an Teilchen an und polymerisiert auf deren Oberfläche weiter. Der Abbruch eines adsorbierten Radikals erfolgt um so seltener, je größer die Oberfläche aller Teilchen ist. Deshalb steigt seine kinetische Kettenlänge und damit die Uneinheitlichkeit des gesamten Polymeren mit dem Umsatz. Der Flächenbedarf eines Radikals hat die erwartete Größenordnung.
Bestimmung der langkettenverzweigung von hochdruckpolyäthylen durch streulicht‐ und viskositätsmessungen
Authors: Casper Rudolf , Biskup Ulrich , Lange Heinz , Pohl Uwe 
Published: April 2003

AbstractLineares und verzweigtes Polyäthylen wurden durch Lösungsmittel‐Gradienten‐Chromatographie fraktioniert. Die Fraktionen wurden durch Streulicht‐ und Viskositätsmessungen charakterisiert und die Beziehungen zwischen Molekulargewicht und Viskositätszahl bzw. Trägheitsradius in α‐Chlornaphthalin bei 127°Cermittelt. Der Exponent in der Beziehung

zwischen dem Verhältnis 〈gη〉Θ der Viskositätszahlen von verzweigten und linearen Fraktionen gleichen Molekulargewichts Mw und dem entsprechenden Verhältnis 〈gη〉Θ,w der Trägheitsradien für Θ‐Bedingungen ergab sich zu

Durch diese Gleichung kann die Langkettenverzweigung von Hochdruckpolyäthylen aus dem in thermodynamisch guten Lösungsmitteln bestimmten Viskositätszahlverhältnis 〈gη〉, das mit dem im Θ‐Lösungsmittel bestimmten 〈gη〉Θ im Rahmen der Meßgenauigkeit übereinstimmt, ermittelt werden. Für die untersuchten verzweigten Polyäthylen‐Fraktionen ergaben sich nahezu unabhängig vom Molekulargewicht etwa 1,4 Langkettenverzweigungen pro 1000 C‐Atome.
Copolymerization of polar vinyl monomers with butadiene in the presence of Lewis acids
Authors: Kuran Witold , Pasynkiewicz Stanisław , Nadir Riad , Kowalewska Barbara 
Published: April 2003

AbstractThe copolymerization of acrylonitrile (AN), methacrylonitrile (MAN), methyl acrylate (MA), and methyl methacrylate (MMA) with butadiene (BD) in the presence of ethylaluminium dichloride, zinc chloride, and stannic chloride was investigated. The reactivity of polar monomers in the copolymerization was found to decrease in the following order: AN>MAN>MMA>MA. It was also found that AN and MAN form with BD copolymers of essentially 1:1 composition; MMA, and particularly MA were found, however, to form with BD copolymers of a composition different from 1:1.In competition with the copolymerization, a Diels‐Alder reaction was shown to occur in the investigated systems. The reactivity of polar monomers in the Diels‐Alder reaction was found to increase in the following order: MAN<AN<MMA<MA. In the presence of aluminium bromide and of antimony chloride these monomers were found to produce with BD the corresponding Diels‐Alder adducts but not the copolymers.The obtained results are discussed in terms of the electron‐accepting properties of polar vinyl monomers and of the stability of transient charge‐transfer complexes between the monomers involved in the copolymerization and the Diels‐Alder reaction.
Linear oligopeptides, 29. Infrared conformational analysis of homo‐oligopeptides in the solid state and in solution
Authors: Palumbo Manlio , da Rin Silvio , Bonora Gian Maria , Toniolo Claudio 
Published: April 2003

AbstractThe IR spectra of eight series of monodisperse, chemically and optically pure, protected linear homo‐oligopeptides having the general formula Boc(LX)nOMe, where X = Ala, Nva, Val, Leu, Ile, Phe, Met, Cys(Me), and n = 2–7, were investigated by IR absorption spectroscopy in the solid state and in solution. The measurement in the solid state indicate that all pentamers and higher oligomers assume essentially a β‐form; trimers and tetramers present evidence of mixtures of β‐ and unordered structures, while in dimers the unordered structure is largely predominant. The occurrence of the unusual intermolecular β‐parallel conformation was suggested for HCl·H(LX)7OMe, where X = Val, Ile, and Phe. Further, the absorbance in the NH stretching region was determined as a function of concentration in deuterochloroform. This conformational analysis in solution showed that a high content of intramolecularly hydrogen‐bonded forms exist in all homo‐tetramers with the exception of those derived from the β‐branched amino acid residues, valine and isoleucine. The effect of the presence of a sulfur atom or an aromatic ring in the amino acid side chain (S‐methyl cysteine, methionine, and phenylalanine peptides) on the stability of the folded forms is also discussed.
Ein Beitrag zur Teilchenbildung bei der Emulsionspolymerisation von Acrylsäure‐ und Methacrylsäureestern
Authors: Sütterlin Norbert , Kurth Hans‐Joachim , Markert Gerhard 
Published: April 2003

AbstractZur Beschreibung der Teilchenbildung bei der Emulsionspolymerisation werden im allgemeinen zwei Denkansätze herangezogen. Gemäß Harkins, Smith und Ewart spielt die mit Monomeren angequollene Emulgatormicelle hierbei die maßgebende Rolle. Nach Fitch und Roe hingegen erfolgt die Teilchenbildung, indem in der Wasserphase gebildete Oligomerenradikale ihr Löslichkeitsgleichgewicht überschreiten.Die Praxis bei der Emulsionspolymerisation von Acrylsäure‐ und Methacrylsäureestern hat gezeigt, daß die Vorstellungen von Fitch‐Roe den wahrscheinlicheren Fall darstellen. Bei einer Betrachtungsweise über ein Lösungs‐Fällungsgleichgewicht ist es naheliegend, der Monomerengleichgewichtskonzentration in der Wasserphase und damit gleichlaufend der Hydrophilie des Polymeren größere Aufmerksamkeit zu widmen.Trägt man die mittlere Teilchenzahl ND pro Einheitsvolumen als Funktion der zu Beginn der Polymerisation vorliegenden Emulgatorkonzentration [E] auf, erhält man in doppeltlogarithmischem Maßstab die bekannten S‐fömigen Abhängigkeiten, in denen die kritische Micellkonzentration des verwendeten Emulgators keinen exponierten Kurvenpunkt darstellt. Die Teilchenzahl für eine bestimmte Emulgatorkonzentration ist dabei von der Sättigungskonzentration [M] der Monomeren in der Wasserphase abhängig.Bei den im allgemeinen viel zu wenig beachteten Agglomerationsvorgängen hat man zwischen einer Primäragglomeration und einer Sekundäragglomeration zu unterscheiden. Besonders bei den hydrophilsten Vertretern der Acrylat‐ bzw. Methacrylatreihe wirken sich diese Agglomerationserscheinungen auf die mittlere Teilchenzahl aus. Eine Ursache dafür dürfte die Emulgatorgleichgewichtskonzentration in der Teilchengrenzenfläche sein, die mit steigender Hydrophilie des Polymerisats abnimmt.
Reaktive mikrogele, 4. Über besonderheiten bei der emulsionspolymerisation von 1,4‐divinylbenzol
Authors: Obrecht Werner , Seitz Ulrich , Funke Werner 
Published: April 2003

AbstractEs wurde die Emulsionspolymerisation von 1,4‐Divinylbenzol mit Natrium‐dodecylsulfat als Emulgator und Kalium‐peroxodisulfat als Initiator untersucht mit dem Ziel, reaktive Mikrogele mit verschiedenen Teilchen‐Durchmessern zu synthetisieren. Gegenüber der Emulsionspolymerisation von Styrol wurden bei 1,4‐Divinylbenzol die Ausbildung von Koagulat, verschiedene Agglomerationsstufen und schließlich eine wesentlich höhere Partikelzahl gefunden. Die möglichen Ursachen der genannten Besonderheiten werden diskutiert.
Tetraaza[14]annulen‐Derivate und ihre Vorstufen, 2. Bicyclische Verbindungen und polymere Substanzen
Authors: Müller Reinhardt , Wöhrle Dieter 
Published: April 2003

Abstract3,3′‐Diaminobenzidin (1) und 1,2,4,5‐Tetraaminobenzol (7) reagieren mit 3,3′‐(1,2‐Phenylen‐1,2‐diimino)dipropenal (2) im Molverhältnis 1:2 zu bicyclischen Tetraaza[14]annulenen 3 bzw. 8 und mit Propinal (4) oder Acetylaceton im Molverhältnis 1:2 zu polymeren Tetraaza[14]annulenen 9 bzw. 10. Durch Komplexierung mit Salzen der zweiwertigen Übergangsmetalle Kupfer, Nickel, Kobalt und Eisen wurden die entsprechenden bicyclischen und polymeren Metallchelate 11a—d, 12a—d und 13a—d, 14a—d dargestellt. Alle Verbindungen wurden durch IR‐, Elektronen‐ und Massenspektren sowie durch Elementaranalysen charakterisiert.
Asymmetric synthesis catalyzed by poly‐L‐alanine
Authors: Ueyanagi Kaoru , Inoue Shohei 
Published: April 2003

AbstractAsymmetric addition of dodecanethiol to isopropenyl methyl ketone catalyzed by the terminal amino group of poly‐L‐alanine (PLA) and its terminal models was studied. When PLA was used as catalyst, the [α]D value of the product, 1‐(dodecylthiomethyl)ethyl methyl ketone, was larger than in the case of catalysis by the terminal models of PLA, indicating the importance of conformation of the polymer catalyst in asymmetric reaction. On the other hand, on addition of ethanol to the reaction system, the [α]D of the product was increased in each case.
Cathodic polymerization of maleic anhydride with N‐methylpyridinium iodide
Authors: Bhadani Suraj N. , Prasad Jagdeo 
Published: April 2003

AbstractThe electrochemical homopolymerization of maleic anhydride was investigated at constant electric current in a divided cell. The polymer yield depended markedly on the quantity of current passed through the solution, polymerization time, and on the nature of supporting electrolytes and solvents. The visible spectra of electrolysed solutions and the IR spectra of poly(maleic anhydride) were measured. The polarographic measurements revealed that N‐methylpyridinium iodide, employed as supporting electrolyte for the polymerization of maleic anhydride, was reduced at a smaller cathodic voltage than maleic anhydride. Under the given reaction conditions the electrolytic reduction products of the salt might have initiated the polymerization. An anionic polymerization mechanism is assumed.
Untersuchungen über poly(arylenvinylen)e, 13. Phenylsubstituierte poly‐p‐xylylidene. Durch UV‐licht induzierte photoleitfähigkeit im NIR
Authors: Hörhold Hans‐Heinrich , Opfermann Johannes 
Published: April 2003

AbstractUV‐Irradiation of phenyl‐substituted poly‐p‐xylylidenes induces photoconductivity in the range of 7000–17000 cm−1. The spectral distribution is identical with that of photoconductivity found in macromolecular radical cations produced chemically by oxidation with antimony pentachloride. This supports the assumption that the induced photoconductivity can be attributed to the photochemical generation (UV) and the optical excitation (VIS/NIR) of macromolecular radical ions.
Vinyl polymerization by metal complexes, 30. On the initiation mechanism of vinyl polymerization by the system copper(II) chelate of poly(vinyl alcohol)/carbon tetrachloride: Spin trapping and gelation studies
Authors: Kimura Keiichi , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractThe initiation mechanism of vinyl polymerization by a copper(II) chelate of poly(vinyl alcohol) was studied in aqueous solution in the presence of carbon tetrachloride, in order to determine the free radical species formed during the initiation step. Trichloromethyl radicals were ascertained to be the main initiation species, by spin trapping and gelation experiments. Differences in polymerization activity between methyl methacrylate and acrylonitrile are discussed.
Unidirectional compression measurements on swollen polystyrene model‐networks
Authors: Belkebir‐Mrani Ahmed , Herz Jean Edouard , Rempp Paul 
Published: April 2003

AbstractThe elastic behavior of swollen polystyrene model‐networks, prepared by anionic block‐copolymerization of styrene with small amounts of divinylbenzene, has been studied by unidirectional compression measurements.The compression modulus G* as defined in the present paper, was related to the structural characteristics of the networks and to the interaction parameters of the systems. The influence of these various parameters on the gel behavior has been discussed.From comparison between uniaxial compression measurements and X‐ray diffraction data on the same gels, it was shown at least qualitatively, that the elastic chain‐interpenetration depends upon the functionality of the crosslinkages.
Partially aromatic polyamides: A calorimetric and dynamic‐mechanical investigation
Authors: Manescalchi Francesco , Pizzoli Maria , Drusiani Annamaria , Zanetti Franca 
Published: April 2003

AbstractSome partially aromatic polyamides were prepared from hexamethylenediamine and the following dicarboxylic acids: 4,4′‐dimethyl‐4,4′‐p‐phenylenedipentanoic acid, 3,3′‐dimethyl‐3,3′‐p‐phenylenedibutanoic acid, 3,3′‐p‐phenylenedibutanoic acid, and 3‐methyl‐3,3′‐p‐phenylenedipropanoic acid. From the dynamic‐mechanical and thermal investigations it appears that the substitution of H‐atoms with methyl groups adjacent to the phenylene ring very little affects the glass transition temperature of the polyamides, but seems to impede chain packing and thus lowering both melting points and crystallinity. The annealing below the glass transition temperature Tg was also explored. The development of endothermic peaks in the glass transition region is interpreted in terms of localized order.
Study of the mechanism of propagation and transfer reactions in the polymerization of olefins by Ziegler‐Natta catalysts, 4. The kinetic scheme for propagation and chain transfer reactions
Authors: Zakharov Vladimir A. , Bukatov Gennadii D. , Chumaevskii Nikolay B. , Yermakov Yurii I. 
Published: April 2003

AbstractOn the basis of the experimental data on the number of propagation centers, activation energy, and rate constants of propagation and transfer reactions, a kinetic scheme for propagation and chain transfer reactions in the polymerization of olefins in the presence of Ziegler‐Natta catalysts is considered. The main features of this scheme are: (a) monometallic composition of propagation centers; (b) two‐stage mechanism of the propagation reaction: (c) the reversible adsorption of an organoaluminium cocatalyst on the titanium of the propagation center resulting in its temporary deactivation and chain transfer with an organoaluminium compound.
Metalloporphyrins in polymeric matrices and in micelles, 2. Iron porphyrins and cobalt porphyrins in copolymers of styrene and 1‐vinylimidazoles
Authors: Fuhrhop Jürgen‐Hinrich , Besecke Siegmund , Vogt Walter , Ernst Josef , Subramanian Japyesan 
Published: April 2003

AbstractCopolymers from styrene and 1‐vinylimidazoles (4a–f), form low spin adducts with iron(II) porphyrins and iron(III) porphyrins, when the content of imidazolyl groups in the polymer is ten mole percent or more. With polymers having a content of imidazolyl groups of less then one mole percent, only high spin adducts are observed. With terpolymers, in which the porphyrin is covalently bound to the copolymer the same phenomenon is observed. Only the high spin Fe(II) porphyrin adducts in the solid state adsorb molecular oxygen like cobalt(II) porphyrins under the same conditions. Adsorptions and desorptions of oxygen are much slower in the cases of iron(II) porphyrins than with the cobalt(II) porphyrins. Electronic and ESR spectra as well as susceptibility measurements were used to characterize the reported spin states.
Pfropfung und vernetzung mittels azogruppen enthaltender copolymerer, 6
Authors: Kerber Robert , Nuyken Oskar , Steinhausen Rainer 
Published: April 2003

AbstractCopolymers containing styrene and 2‐(4‐vinylphenylazo)‐2‐methylmalononitrile units were grafted with acrylonitrile. It was found that kinetically this reaction behaves similar to the acrylonitrile polymerisation initiated by low‐molecular azocompounds. The reaction products were fractionated into graft‐copolymer, ungrafted backbone‐polymer and polyacrylonitrile. The characteristic values for the grafting reaction (ε, UG, π) were determined.
Synthesis of poly(3‐vinyl‐1,4‐butyrolactone‐co‐acrylonitrile)
Authors: Shimidzu Takeo , Yoshikawa Masakazu , Chiba Hisashi , Murakami Akira 
Published: April 2003

AbstractCopolymerizations of 3‐vinyl‐1,4‐butyrolactone (1) and acrylonitrile (2) initiated by dibenzoyl peroxide or 2,2′‐azoisobutyronitrile were carried out. The following reactivity ratios were found for the bulk copolymerization at 70°C for 1: r1 = 0,078±0,037 and for 2: r2 = 4,7±0,3. In addition the values Q1 = 0,033 and e1 = 0,053 were obtained. The ring opening and the ring closing of the lactone moiety in the polymer with an alkaline and an acid were found to be reversible.
Interaction between dyes and polyelectrolytes, 7. Metachromatic behavior of methylene blue induced by poly(sodium acrylate) and its homologues
Authors: Shirai Masamitsu , Murakami Yoshihiro , Tanaka Makoto 
Published: April 2003

AbstractThe structural effect of polyanions on the metachromatic behavior of methylene blue (1) was investigated spectrophotometrically. The following polyanions were used: poly(sodium acrylate) (PAA), conventional poly(sodium methacrylate) (a‐PMA), isotactic poly(sodium methacrylate) (i‐PMA), syndiotactic poly(sodium methacrylate) (s‐PMA), and the copolymer poly(sodium maleate‐covinyl alcohol) (1:1) (PMVA). The metachromatic behavior was followed by the changes in the molar absorption coefficient (ε) at 664 nm of methylene blue (1) and in the wave length (λm) of the metachromatic band. Important factors for metachromasy were found to be the flexibility and charge density of the polymer. Differences between OSO and COO⊖ as binding sites are discussed.
Study of the isothermal bulk polymerization of diallyl fumarate and related compounds by differential scanning calorimetry
Authors: Černec Franc , Osredkar Uči , Može Adolf , Vizovišek Ivan , Lapanje Savo 
Published: April 2003

AbstractCourse and kinetics of the isothermal bulk polymerization of diallyl fumarate and the course of the polymerization of diallyl fumarate, diallyl maleate, and diallyl succinate by programmed heating were studied. 2,2′‐Azoisobutyronitrile was used as initiator. The isothermal bulk polymerization was investigated at temperatures between 75 and 96°C and initiator concentrations ranging from 22,5 to 62,5 mmol/dm3 were applied. The bulk polymerization by programmed heating was investigated at temperatures between 40 and 190°C and at constant initiator concentration of 62,5 mmol/dm3. The negative value of the heat of isothermal bulk polymerization of diallyl fumarate at 75°C at the initiator concentration of 22,5 mmol/dm3 was found to be −63,6 kJ/mol and to increase with increasing temperature to −87,9 kJ/mol at 96°C. Also an increase was observed at higher initiator concentrations in the same temperature range. The initial rate constants for the isothermal bulk polymerization of diallyl fumarate were determined and from them the overall activation energy (100,4 kJ mol). It was found that the overall rate of polymerization at low degrees of conversion depends on the square root of the initiator concentration. The heats of the polymerization by programmed heating at constant initiator concentrations for diallyl fumarate, diallyl maleate, and diallyl succinate were found to be −126,4, −82,9, and −90,8 kJ/mol, respectively. In all cases the DSC‐curves display two peaks. On the basis of the results obtained, it was possible to interpret the differences in reactivity of individual functional groups in these compounds observed in programmed heating.
Étude par 13C NMR et 1H NMR du dextrane et de ses dérivés acétylés et benzylés
Authors: Gagnaire Didier , Vignon Michel 
Published: April 2003

AbstractA 13C NMR and 1H NMR study has been performed on a bacterial dextrane, its triacetylated derivative and a synthetic tri‐O‐benzyldextrane obtained by polycondensation. The main feature of these three products is their regular linearity of glucose residues linked α‐D‐(1→6). In each of them, the proton signals were assigned by homonuclear double irradiation and the 13C signals by selective proton irradiation.The 13C chemical shifts of isomaltose and gentiobiose are compared with the shifts of the corresponding homopolymers dextrane and pustulane.
Zur fraktionierung von polymeren durch direktextraktion
Authors: Holtrup Wolfgang 
Published: April 2003

AbstractA method of solution fractionation by direct extraction is described for the purposes of determining molecular weight distributions and preparing almost monodisperse fractions. Unexpectedly, rapid phase equilibration is obtained by vigorous vibrational agitation of powdered polymers in corresponding solvent systems. In the case of high density polyethylene, phase equilibration proceeds within 5 min and is independent of particle size up to a diameter of 1 mm. Molecular weight distributions determined by the direct extraction technique deviate only slightly from those obtained by conventional gel permeation chromatography. Besides polyethylene also other well‐known polymers were fractionated by this method. It is especially well applicable to partially crystalline polymers, but less applicable to amorphous polymers.
Carbon‐13 NMR spectra and reactivities of vinyl compounds in ionic and radical polymerizations
Authors: Hatada Koichi , Nagata Kazuhiko , Hasegawa Toshihiko , Yuki Heimei 
Published: April 2003

AbstractThe 13C‐chemical shift of β‐carbon in the vinyl group of monomers was correlated with the relative reactivity of the monomer in the cationic copolymerizations of substituted styrenes, benzyl vinyl ethers, and phenyl vinyl ethers and also in the copolymerization of substituted styrenes by Ziegler catalysts. It was found that the β‐carbon resonates at the higher field, the higher the reactivity of the monomer is. The reverse was the case in the anionic addition reaction of substituted styrene to living polystyrene. The relations were also studied between the 13C‐chemical shift and the e‐value of the monomer and some direct evidence was obtained for the validity of the Q–e scheme. From these results it was revealed that the 13C‐chemical shift of vinyl compounds is an important tool for the examination of the mechanism of polymerization reaction.
Vernetzte polymere mit spaltbaren netzbrücken, 5. Homopolymerisation von 4‐vinylbenzoesäureanhydrid
Authors: Braun Dietrich , Brendlein Wolfgang , Jung Jin Chul 
Published: April 2003

AbstractThe kinetics of the crosslinking homopolymerization of symmetrical diolefines with independent double bonds is described. Experiments are carried out with 4‐vinylbenzoic anhydride. The experimental results are compared with the theory and the discrepancy is discussed.