bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalyse de transformation des oléfines par les complexes du tungstène, 4. Evolution de la distribution des masses moléculaires au cours de la polymérisation des cyclooléfines
Authors: Arlie Jean‐Pierre , Chauvin Yves , Commereuc Dominique , Soufflet Jean‐Pierre 
Published: April 2003

AbstractOn a étudié, au moyen de la chromatographie d'exclusion en phase liquide (GPC) l'évolution, en fonction du temps, de la distribution des masses moléculaires du polypenténamère et du polyocténamère obtenus au moyen de catalyseurs à base de tungstène.Le polypenténamère présente une simple distribution dont le maximum et la polymolécularité diminuent avec l'avancement de la réaction.Le polyocténamère préparé soit à partir du cyclooctène soit à partir d'un polymère de haute masse moléculaire présente une double distribution qu'on peut considérer comme la somme de deux distributions simples et dont les proportions relatives sont indépendantes de l'avancement de la réaction. Ces deux distributions tendent à devenir «log‐normales» avec l'avancement.Le co‐polymère cyclopentène‐cyclooctène présente également une double distribution, les oligomères comportant à la fois des unités octénamère et penténamère.La formation simultanée des hauts polymères et des oligomères est interprětée sur la base d'une réaction de polyaddition sur une liaison métallo‐carbènique avec transfert de chaǐne intramoléculaire.
Thermodynamics of the stereosequence propagations in the radical polymerization of vinyl chloride studied by 13C‐NMR and IR
Authors: Pham Quang‐Tho , Millan Jose‐Luiz , Madruga Enrique Lopez 
Published: April 2003

AbstractThe variation of the tacticties of radical poly(vinyl chloride)s as a function of the polymerization temperatures has been examined by 13C‐NMR (in terms of triads and tetrads) and IR (in terms of dyads). It has been observed that BERNOUILLIan statistics could be verified at 0°C for radical polymerization in bulk. The calculated values of differential enthalpies and entropies of activation revealed that, relatively, radical poly(methyl methacrylate)s propagate more easily in syndiotactic placement than radical poly(vinyl chloride)s.
Oligooctenamere, charakterisierung und massenspektrometrische untersuchungen
Authors: Höcker Hartwig , Musch Rüdiger 
Published: April 2003

AbstractDie homologe Reihe der Oligomeren des Cyclooctens wurde mit Hilfe der Metathese‐Reaktion dargestellt; die Oligomeren wurden gelchromatographisch getrennt und gereinigt. Ihre Siedepunkte und Brechungsindices wurden bestimmt, und ihr spektroskopisches Verhalten wurde untersucht. Insbesondere werden die Massenspektren der Oligomeren im Vergleich zu denen der Oligomeren des Cyclododecens, des 1,5‐Cyclooctadiens und acyclischer Oligobutadiene diskutiert. Die Ergebnisse bestätigen die cyclische Struktur der durch ringöffnende Polymerisation von Cycloolefinen erhaltenen Oligomeren. Darüberhinaus wird gezeigt, daß die Massenspektrometrie unter geeigneten Bedingungen herangezogen werden kann, um zwischen cyclischen und acyclischen Kohlenwasserstoffen zu unterscheiden.
Polymérisation par ouverture de cycle, 2. Polymérisation des dihalo‐9,9‐bicyclo[6.1.0]nonène‐4
Authors: Pinazzi Christian P. , Cattiaux Jacques , Pleurdeau Alain , Brosse Jean‐Claude 
Published: April 2003

AbstractLa polymérisation par métathèse des dihalo‐9,9 bicyclo [6.1.0] nonène‐4 (dichloro‐9,9 (1a) et dibromo‐9,9 bicyclo[6.1.0] nonène‐4 (1b)) conduit à des polymères dont l'unité monomère est constituée par une alternance de motifs butadièniques‐1,4 et gem‐dihalocyclopropaniques situés entre deux groupements méthyléniques. Cependant, les compoés obtenus présentent une certaine proportion de motifs de structure bicyclique correspondant à une réaction de type transannulaire. Lorsque le benzène est utilisé comme solvant, les polymères comportent des groupements aromatiques substitués en proportions non négligeables correspondant à la fixation de benzène par réaction de Friedel et Crafts dans le cas où la polymérisation procède selon un mécanisme transannulaire. Les études systématiques ont permis de déterminer les importances relatives de ce type de réaction secondaire.
Über mehrparameterkorrelationen der kationischen polymerisation von vinylmonomeren: Polylinearitäten
Authors: Heublein Günther , Dawczynski Horst , Hallpap Peter 
Published: April 2003

AbstractFür die kationische Polymerisation vonp‐substituierten Styrolen konnten die experimentellen Zielgrößen, Bruttogeschwindigkeitskonstanten logkBruttound Durchschnittspolymerisationsgrade logDP, in linearen Mehrparametergleichungen mit Parametern für den Einfluß der Monomerstruktur, des Lösungsmittels und des Katalysator/Cokatalysatorsystems verknüpft werden. Die erhaltenen Gleichungen gestatten Vorhersagen für die genannten Zielgrößen mit Abweichungen kleiner 10%.
High 1,4‐cis‐polybutadiene by uranium catalysts, 1. Tris(π‐allyl)uranium halide catalysts
Authors: Lugli Gabriele , Mazzei Alessandro , Poggio Sergio 
Published: April 2003

AbstractThe synthesis of tris(π‐allyl)uranium halides (2a–c) and their behaviour in the stereospecific polymerization of butadiene are reported. Independently from the nature of the halogen bound to uranium, very high 1,4‐cis‐polymer with a fairly good yield is obtained. The catalytic activity of allyluranium derivatives is very much improved when a Lewis acid is added as a co‐catalyst. It is characteristic of the polymer to show a cis‐content up to 99% and an exceptionally high chain regularity at least for long chain sequencies.
Über eine polymeranaloge umsetzung zur darstellung von 1‐phenyl‐1‐(4‐vinylphenyl)äthylen/styrol‐copolymeren
Authors: Braun Dietrich , Traser Günter 
Published: April 2003

Abstract1‐Phenyl‐1‐(4‐vinylphenyl)äthylen(PVPÄ)/Styrol‐Copolymere mit verschiedenem Gehalt an PVPÄ‐Grundbausteinen wurden durch polymeranaloge Reaktion aus 4‐Vinylbenzophenon(VBP)/Styrol‐Copolymeren mit Methylmagnesiumjodid hergestellt. Zur Charakterisierung der Copolymeren wurden die Molekulargewichte mit Hilfe der Osmometrie und der Lichtstreuung bestimmt; die Grenzviskositätszahlen der Copolymeren wurden gemessen. Die Ergebnisse zeigten, daß bei den Copolymeren bis zu einem Gehalt von 10 Mol‐% an VBP‐Grundbausteinen praktisch keine Änderungen im Molekulargewicht und den Grenzviskositätszahlen nach der Umsetzung auftreten und die Reaktion somit echt polymeranalog verläuft. Bei einem Gehalt von 20 Mol‐% an VBP ist eine merkliche Erhöhung des Molekulargewichts und der Grenzviskositätszahl zu beobachten, während bei 50 Mol‐% an VBP die Copolymeren nach der Umsetzung nicht mehr in DMF löslich sind und Mikrogele enthalten.
Heterogeneous nucleation and growth of spherulites from a polycaprolactone (poly(1‐oxy‐6‐oxohexamethylene)) melt
Authors: Goldfarb Louis , Garrett Thomas B. , Rittenhouse James R. , Messersmith David C. 
Published: April 2003

AbstractA kinetic crystallization study of polycaprolactone (poly(1‐oxy‐6‐oxohexamethylene) (1)) has been initiated to investigate the primary nucleation and primary spherulitic growth from a polymer melt at temperatures that are high enough to insure nucleation‐limited crystallite growth. The analysis of the kinetic data is largely made on the basis of an Avrami model which proved to be well suited for the interpretation of the crystallization of 1.
Acrylic acid popcorn polymers
Authors: Breitenbach Johann W. , Kauffmann Harald F. 
Published: April 2003

AbstractPoly(acrylic acid) is not soluble in the pure monomer. In the polymerization of acrylic acid in bulk, both glassy and opaque polymer is obtained but no popcorn polymer. Formation and proliferation of popcron polymer takes place during polymerization by adding water to the monomer. The better solvent quality of the monomer/water mixture for poly(acrylic acid) compared to the solvent quality of pure monomer is considered to be the cause for popcorn polymer formation.
The intrinsic viscosity of poly(acrylic acid) at different ionic strengths: Random coil and rigid rod behaviour
Authors: Kay Peter J. , Treloar F. E. 
Published: April 2003

AbstractThe intrinsic viscosities of low molecular weight fractions of atactic poly(acrylic acid) at 50% and 100% neutralization and at several concentrations of added sodium chloride is studied. In salt‐free solutions the 100% neutralized polymer assumes the rigid rod form. The results at concentrations of sodium chloride higher than 0,02 mol/l can be interpreted in terms of a non‐draining random coil polymer.The values of KΘ are determined using the Stockmayer‐Fixman method; there is an increase in KΘ on going from poly(acrylic acid) in dioxane through the 50% neutralized form in 0,5M sodium chloride solution to the 100% neutralized form in 1,5M sodium chloride solution, indicating the continued effect of short‐range electrical forces at the Θ‐point.
New catalysts for the oxidative polymerization of 2,6‐dimethylphenol. Bis(1,2‐dicyanoethylene‐1,2‐dithiolato)cuprate(2‐) complexes
Authors: Kaneko Masao , Manecke Georg 
Published: April 2003

AbstractThe catalytic activities of various bis(1,2‐dicyanoethylene‐1,2‐dithiolato)metal (1a–f) complexes were investigated. It was found that copper bis(1,2‐dicyanoethylene‐1,2‐dithiolato)cuprate(2‐) (1a) catalyzes the oxidative polymerization of 2,6‐dimethylphenol in the presence of molecular oxygen. At some polymerization conditions this catalyst is much more active than the well‐known copper(II)‐pyridine complex.
Modellbetrachtung zur Radikalausbeute bei der radikalischen Polymerisation
Authors: Mayer Gunter 
Published: April 2003

AbstractDie kinetisch wirksame Radikalausbeute ist eine chemisch und diffusionskontrollierte Größe. Der Grad der jeweiligen Kontrolle ist systemspezifisch. Die chemische Kontrolle geht hauptsächlich von der Kettenstartreaktion, die Diffusionskontrolle von der Primärradikalrekombination aus. Die entwickelte Modellvorstellung erfaßt diese konkurrierenden Einflüsse. Mittlere Diffusionswege der Primärradikale bis zu ihrer Rekombination werden abgeschätzt.
Autoxydation radio‐induite du poly(oxyéthylène) en solution aqueuse, 7. Cinétique de la consommation d'oxygène
Authors: Decker Christian , Marchal Jean 
Published: April 2003

AbstractOn a étudié l'autoxydation du poly(oxyéthylène) radio‐induite en solution aqueuse à 25°C en suivant la consommation d'oxygène, l'accumulation des produits d'oxydation et la production des coupures des chaǐnes. Les résultats montrent que la quasi‐totalité de l'oxygène consommé se retrouve bien sous forme liée dans les produits d'oxydation qui ont été détectés et dosés. Ils montrent aussi que les quantités d'oxygène consommées par l'hydroperoxydation et la dégradation oxydante du polymère sont équivalentes.
Activity of a new polyoxime‐copper complex in the reversible uptake of molecular oxygen and carbon monoxide, in the polymerization of acrylonitrile, and in the addition reaction of alcohols to acrolein
Authors: Kim Sung Jho , Takizawa Takeo 
Published: April 2003

AbstractA new polyoxime‐copper complex was prepared from cupric acetate and a polyoxime which is considered to consist largely of 1,2‐bis(hydroxyimino)trimethylene units. The properties of the complex were studied. Its ESR spectrum was found to be similar to that of the low molecular weight copper(II) complex, whose intensity decreases with increasing copper content. The complex shows a catalytic activity in the Michael type addition reaction of alcohols to acrolein, yielding exclusively β‐alkoxypropionaldehyde. In addition, it initiates the polymerization of acrylonitrile under hydrogen pressure (40 to 90 kg/cm2). Furthermore, the complex with a composition ratio Cu: OX ≈ 1:4 (Cu: number of copper atoms, OX: number of hydroxyimino groups in the complex), after being treated with hydrazine hydrate in methanol under nitrogen, can reversibly take up and release ca. 3,2dm3 of molecular oxygen (in water) and 0,8dm3 of carbon monoxide (in methanol) per mole of copper. These activities decrease remarkably with decreasing copper content of the complex.
Kinetics of styrene polymerization initiated by boron trifluoride diethyl etherate in the presence of π‐electron acceptors
Authors: Velichkova R. S. , Panayotov I. M. 
Published: April 2003

AbstractThe kinetics of the polymerization of styrene in 1,2‐dichloroethane, initiated by boron fluoride diethyl etherate (1), was studied in the presence of small amounts of tetracyanoethylene (2) or 1,3,5‐trinitrobenzene (3). The reactions are of second order with respect to the monomer and of first order with respect to the catalyst. Addition of the π‐electron acceptors 2 or 3 increased the polymerization rate without affecting the concentration‐dependences of the system. In the presence of 2 the activation energy decreased from 11,4 kcal/mol (47,7 kJ/mol) to 6,9 kcal/mol (28,8 kJ/mol). The decomposition of the styrene/2‐complex in the presence of 1 was demonstrated. The results from the kinetic and conductometric measurements showed that the increase in the polymerization rate at the addition of the acceptors 2 (or 3) was probably mainly due to an increase of the concentration of free ions.
Orientation of propylene units in polypropylene and ethylene/propylene copolymers
Authors: Locatelli Paolo , Immirzi Attilio , Zambelli Adolfo , Palumbo Rosario , Maglio Gianni 
Published: April 2003

AbstractEthylene‐propylene copolymers prepared with syndiotactic specific catalysts contain both head‐to‐tail and tail‐to‐head oriented propylene units. Consequently, this copolymerization is, actually, a terpolymerization, and the propylene polymerization is a binary copolymerization.The consequences of this fact on the kinetics of polymerization and copolymerization are considered.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 1, synthèse de polyisoprènes
Authors: Pinazzi Christian , Legeay Gilbert , Brosse Jean‐Claude 
Published: April 2003

AbstractLe peroxyde d'hydrogène (eau oxygénée) se décompose sous l'action de la chaleur en deux radicaux hydroxyles amorceurs d'un processus de polymérisation: cette réaction effectuée sur l'isoprène, conduit d'une part à des polymères liquides à extrémités hydroxylées de structure essentiellement 1,4 trans, et d'autre part, à des oligomères constitués d'une à quatre unités mères. L'addition au milieu réactionnel d'un alcool en quantité plus ou moins importante permet de faire varier les taux de conversion en oligomères et en polymères, ainsi que les masses moléculaires moyennes de ces derniers. Diverses études systématiques mettent en évidence l'influence du temps de réaction et de la température sur les résultats de la polymérisation.
Kinetics of oxidative polymerization of 1,8‐nonadiyne
Authors: Kevelam Hendrik J. , de Jong Klaas P. , Meinders Herman C. , Challa Gerrit 
Published: April 2003

AbstractA study was made of the influence of the concentrations of catalyst, monomer, water, ligand, and oxygen on the rate of oxidative polymerization of 1,8‐nonadiyne (1) at 26°C in the presence of homogeneous catalysts derived from cuprous chloride (copper(I) chloride) and tertiary amines. In the initial stages the reaction is nearly first order in [Cu2Cl2] up to the solubility limit of the active catalyst, and second to first order in [1] for low to medium monomer concentrations. The reaction rate decreases with increasing water content and is enhanced by increasing ligand concentration and increasing basicity of the ligand: triethylamine (TEA) > N,N,N',N'‐tetramethylethylenediamine (TMED) > pyridine. On the basis of these kinetic results and a study of the catalyst structure a reaction scheme is proposed. In this scheme the formation of water occurs in reversible reaction steps from acetylenic endgroups and a dimeric copper(II) complex [TMED. Cu(OH)] · 2Cl−, followed by intramolecular oxidative coupling of two complexed acetylide ions.
Über makrozwitterionen, 10. Versuche zur darstellung von makrozwitterionen aus α,ω‐bifunktionellem poly(α‐methylstyrol)
Authors: Eisenbach Claus D. , Schnecko Hans , Kern Werner 
Published: April 2003

AbstractVerschiedene Möglichkeiten zur Darstellung von Makrozwitterionen ohne polare Gruppen in der Polymerkette werden diskutiert.Unter Verwendung von 3‐Dimethylaminopropyllithium als Initiator und Propansulton (2) als Kettenabbruchreagenz wurden α,ω‐bifunktionelle Poly(α‐methylstyrol)e 4 mit einer tert. Amino‐ und einer Lithiumsulfonat‐Endgruppe (Molekulargewichtsbereich ≈ 103; Bifunktionalität >90%) dargestellt. Die beiden Endgruppen wurden wie bei den entsprechenden monofunktionellen Polymeren analytisch (N,S) und spektroskopisch (IR und NMR) nachgewiesen.Obwohl die beiden Endgruppen der bifunktionellen Polymeren jeweils unabhängig in die freie Sulfonsäure‐Gruppe bzw. in die Trimethylammoniumjodid‐Gruppe quantitativ überführt werden konnten, gelang es nicht, im jeweils letzten Reaktionsschritt, Makrozwitterionen 8 zu erhalten: Die Sulfonsäure 5 lagerte sich entgegen den Erwartungen nicht oder kaum in Zwitterionen 3 um, so daß bei der Reaktion mit Diazomethan statt des Betains hauptsächlich der Sulfonsäure‐methylester entstand; außerdem trat weitgehender Verlust der Aminogruppe ein. Bei dem Poly(α‐methylstyrol) mit quart. Ammoniumjodid‐ und Lithiumsulfonat‐Endgruppe 7 wurde nach Abtrennung der Gegenionen (J⊖ durch Ag2O und Li⊕ durch Kationenaustausch) ebenfalls ein weitgehender Abbau der Ammonium‐Endgruppe festgestellt.
Gel permeation chromatography with crosslinked polystyrene gels and poor and theta solvents for polystyrene, 1. Universal calibration for cyclohexane at 35°C
Authors: Dawkins John V. , Hemming Malcolm 
Published: April 2003

AbstractGel permeation chromatography calibrations for polystyrene (PS) standards, poly(dimethylsiloxane), (PDS) fractions, and polyisoprene, (PI) samples have been obtained with a combination of four columns packed with crosslinked polystyrene gels using chloroform and cyclohexane as eluents at 35°C. Chloroform is a good solvent for all three polymers which separate according to steric exclusion, since they follow the same plot of log hydrodynamic volume vs. retention volume VR. Cyclohexane is a theta solvent for PS, but a good solvent for the other two polymers. PDS and PI in cyclohexane follow the same plot of log hydrodynamic volume vs. VR, but the plot for PS in cyclohexane is displaced to high VR values, the displacement increasing as VR increases. PS in cyclohexane gel permeation chromatograms are broader than the PS in chloroform chromatograms, the additional broadening increasing as the PS molecular weight decreases, i. e. as VR increases. Both the additional retention and broadening are explained by solute‐gel interactions, arising because PS prefers the polystyrene‐like gel environment rather than the mobile phase which is a theta solvent. The dependence of solute‐gel interactions, leading to partition and adsorption effects, on the polarity of the eluent is discussed.
Permeability study on adsorption phenomena of poly(vinyl acetate) in well defined porous media
Authors: Gramain Philippe 
Published: April 2003

AbstractThe thickness of layers of poly(vinyl acetate) (PVAC) adsorbed on cellulose filters was studied using a method derived from the viscosity technique developed by Rowland and Eirich. The study was carried out on a series of PVAC samples with molecular weights ranging from 21000 to 2400000. The extension of the adsorbed polymer increases slowly with time and reaches a steady state value after some days. This equilibrium extension increases with increasing solution concentration indicating a competition for adsorption sites between the molecules. For the same concentration, the layer thickness is proportional to the intrinsic viscosity of the polymer. The influence of the pore size is clearly demonstrated: the layer thickness decreases as soon as the size of pores becomes of the same order of magnitude as the hydrodynamic volume of the polymer molecules. For a polydisperse polymer, it is necessary to take into account the molecular weight distribution and the effective concentration inside the pores.
Stereochemistry of the copolymerization of carbon dioxide with optically active phenylepoxyethane
Authors: Hirano Takashi , Inoue Shohei , Tsuruta Teiji 
Published: April 2003

AbstractThe stereochemistry of the copolymerization of optically active phenylepoxyethane (5) with carbon dioxide using a diethylzinc/water system as catalyst was investigated. The optically active copolymer, poly(oxycarbonyloxy‐2‐phenylethylene) (1), was hydrolyzed and the oxy‐2‐phenylethylene unit was isolated in the form of 1,2‐bis(trimethylsilyloxy)‐1‐phenylethane (3). The determination of the optical activity of this ether led to the conclusion that the ring opening of 5 takes place predominantly at the methineoxygen linkage accompanying an inversion in the copolymerization. This fact is in sharp contrast with the stereochemistry of the copolymerization of carbon dioxide with 1,2‐epoxypropane in which the ring opening takes place at the methylene‐oxygen linkage.
Effects of photo‐degradation on the permeability and diffusivity characteristics of poly(p‐methylstyrene)
Authors: Greenwood Robert , Weir Neil 
Published: April 2003

AbstractDiffusion and permeability coefficients for O2 and CO2 were determined for poly‐(p‐methylstyrene) films which have been exposed to short wave (λ=253,7 nm) ultra violet radiation, both in vacuum and at varying pressures of oxygen. It was found that both diffusion and permeability coefficients decrease with increasing exposure to the radiation, the decrease in the vacuum irradiated films being significantly greater than those observed during irradiation in oxygen, presumably a result of higher cross‐linking in the absence of oxygen.Solubility coefficients for polymers irradiated both in oxygen and in vacuum increase non‐linearly on irradiation time. Activation energies and pre‐exponential factors for diffusion increase with increasing degradation. Decreased permeabilities and diffusivities and increasing Arrhenius parameters are discussed in terms of the free volume theory of diffusion—the free volumes decreasing as a result of polymer modification, e.g. crosslinking during degradation—and the energy required to create the necessary critical free volume for a gas molecule to make a diffusive jump, increasing with degradation.
Permanganate‐malic acid redox pair as the initiating system in the homogeneous polymerization of acrylamide
Authors: Misra Gauri S. , Rebello Joseph J. 
Published: April 2003

AbstractThe homogeneous polymerization of acrylamide initiated by the new redox system permanganate‐malic acid was investigated in aqueous media under nitrogen at 35±0,2°C. Over a wide range of concentration (2,5 to 30 mmol dm−3) of the activator (malic acid), (4), the polymerization rate remains unaffected. Addition of sulfuric acid (0,1 to 5 mmol dm−3) increases the rate but decreases the maximum conversion. The value 0,53 of the catalyst exponent confirms a bimolecular termination mechanism. The variation of the rate at a low monomer concentration is linear. The initial rate and the conversion increase with increasing temperature. The activation energy is found to be 82,20 kJ/mol (19,74 kcal/mol) in the temperature range of 25 to 50°C. Neutral salts, water miscible organic solvents, and ethylenediaminetetraacetic acid all suppress both the limiting conversion and the rate of polymerization. The addition of more catalyst at intermediate stages as well as the addition of MnSO4 raise the initial rate and the conversion. Sodium fluoride enhances the rate but lowers the limiting conversion.