bluuebunny/crossref_metadata_2025 huggingface dataset:
Copolymer statistics during esterification of syndiotactic poly(methacrylic acid) with diazotoluene and diazodiphenylmethane
Authors: Strasilla Dieter , Klesper Ernst
Published: April 2003

Syndiotactic poly(methacrylic acid) has been partially esterified with diazotoluene or diazodiphenylmethane in extension of work carried out with diazomethane1. The sequence statistics of the resulting cosyndiotactic benzyl methacrylate–methacrylic acid and diphenylmethyl methacrylate–methacrylic acid copolymers have been studied with 1H‐NMR spectroscopy, by relating the triad probabilities obtained by employing different NMR solvents. For both types of copolymers BERNOULLIan triad statistics were found within accuracy of the NMR measurements. Therefore, these polymer analogous reactions, like the reaction of diazomethane with syndiotactic poly(methacrylic acid)1, are not influenced by a kinetic neighboring group effect, despite the greater space requirement of the two diazoalkanes when compared to diazomethane. The copolymers possess therefore a simple, and defined configurational and compositional structure which cannot be obtained at present by the copolymerization of monomers. The polyelectrolyte character of the copolymers could be eliminated without altering the configurational and compositional statistics by complete esterification with a second diazoalkane. Thus the diphenylmethyl methacrylate–methacrylic acid copolymers were converted with diazomethane to diphenylmethyl methacrylate–methyl methacrylate copolymers and with diazotoluene to diphenylmethyl methacrylate–benzyl methacrylate copolymers. Furthermore, it appears that the reaction with syndiotactic poly(methacrylic acid) may also be utilized to prepare defined cosyndiotactic copolymers composed of three or four different types of monomeric units by successive partial esterification with different diazoalkanes.
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

On 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

The 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

Die 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

La 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

Für 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

The 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

1‐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

A 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

Poly(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

The 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

The 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

Die 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

On 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

A 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

The 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

Ethylene‐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

Le 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

A 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

Verschiedene 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

Gel 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

The 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

The 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

Diffusion 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

The 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.
Studies on polymerizations initiated by syncatalytic systems based on aluminium organic compounds, 4. Polymerization of isobutene initiated by diethylaluminium chloride and chlorine
Authors: Cesca Sebastiano , Giusti Paolo , Magagnini Pier Luigi , Priola Aldo
Published: April 2003

The polymerization of isobutene, initiated by diethylaluminium chloride + chlorine, was studied with the main goal of clarifying the influence of the concentration of the different reagents, the temperature, and the nature of the solvent on the rate of polymerization and on the molecular weight of the products. A kinetic study carried out in methyl chloride at −45°C and with a monomer concentration of 0,1 mol/l, has shown that the polymerization is characterized by a relatively slow initiation which gives the conversion curves an S‐shape. Experiments with successive monomer additions showed that the polymerization of the second and subsequent portions of monomer occurs without acceleration and with a much higher rate. This shows that termination reactions are almost negligible.

The degree of polymerization depends mainly on the transfer reactions with substances having concentrations proportional to those of the components of the syncatalytic system; transfer with monomer is absent, which is a very unusual feature.
Solvent effects on radical polymerization of cyclododecyl acrylate, 2. Copolymerization
Authors: Daimon Hiroshi , Kumanotani Ju
Published: April 2003

The radical copolymerization of cyclododecyl acrylate (CDA) with styrene (St) or acrylonitrile (AN) was studied in bulk, benzene, tetrahydrofuran, or dioxane at 60°C, and was compared with that of cyclohexyl acrylate (CHA).

In the copolymerization with St, the change in the ester groups or the used solvents influenced the reactivity of both acrylates in the same manner as their homopolymerization rates. Approximately, CDA and CHA behaved like methyl methacrylate in the copolymerization with St.

Contrary, in the cases of copolymerization of CDA with AN, peculiar results were obtained and interpreted in terms of characteristic association states of the monomers in the solutions. In benzene solution both the monomer reactivity ratios, r1 and r2, are larger than unity (M1 = AN, M2 = CDA; r1 = 1,7, r2 = 2,0).
Structural aspects of small peptides. Synthesis and characterization of protected homo‐oligomers derived from L‐alanine
Authors: Bonora Gian Maria , Nisato Dino , Toniolo Claudio
Published: April 2003

A series of protected L‐alanine homo‐oligomers from dimer to heptamer was prepared by the dicyclohexylcarbodiimide and acyl azide coupling methods. In the course of the synthetic approach tert‐butoxycarbonyl as the N‐protecting and methyl ester as the C‐protecting end groups were employed. The monodisperse oligomers prepared in this manner were characterized and found to be chemically pure. A polarimetric investigation in a structure disrupting solvent also indicated that all reactions proceeded with complete retention of the configuration. In addition, the dependence of the experimental molar rotation values at 589 nm of L‐alanine internal residues in a polypeptide in a statistical coil conformation on the end groups of the molecule and the solvent is emphasized.
Studies on functional micelles, 4. Effect of alkyl chain length on the micellar reaction of thioalanine S‐alkyl esters
Authors: Kawabata Yasuziro , Kinoshita Masayoshi
Published: April 2003

S‐Hexadecyl, S‐dodecyl, S‐decyl, and S‐octyl esters of thioalanine (1e, 1d, 1c, and 1b) were prepared and reacted at a concentration range of 2,5·10−3 to 1·10−1 mol/l in water with pyridine as a base catalyst to give the cyclic dimer of alanine, 3,6‐dimethyl‐2,5‐piperazinedione (2). The yields of 2 from 1e and 1d were similar within this concentration range, whereas the yield of 2 from 1b rapidly decreased in the concentration range from 1·10−1 to 1·10−2 mol/l, and no dimer 2 was obtained at 2,5·10−3 and 5·10−3 mol/l. These results support the proposed micellar mechanism in the condensation of thioalanine S‐alkyl esters in water.
Étude viscosimétrique du système ternaire polystyrène/poly(méthacrylate de méthyle)/p‐xylène
Authors: Dondos Anastasios , Benoit Henri
Published: April 2003

Dans ce travail sont présentés quelques résultats expérimentaux et quelques considérations théoriques concernant l'indice limite viscosimétrique du polystyrène, (PS), dissous dans un mélange de poly(méthacrylate de méthyle), (PMMA), et de p‐xylène, et de PMMA dissous dans un mélange de PS et de p‐xylène. A une concentration relativement basse, on peut essayer d'interpréter ces systèmes en faisant appel au formalisme des solutions diluées et en introduisant un coefficient d'interaction bAB entre les deux polymères A et B. Cette voie, qui semble la plus simple, est difficile à utiliser quantitativement. car měme pour des concentrations modérées, il faut considérer des termes d'ordre supérieur.

Les résultats obtenus peuvent ětre expliqués par une diminution des dimensions du polymère qui est plus prononcée quand le «polymère‐solvant» est de petite masse moléculaire.

A une concentration élevée, il apparaǐt un point critique qui semble se manifester quand le volume total de la solution est occupé par les deux polymères.
Comparison of successive solutional fractionation with successive precipitational fractionation
Authors: Kamide Kenji , Miyazaki Yukio
Published: April 2003

An attempt was made to compare successive solutional fractionation (SSF) with successive precipitational fractionation (SPF) in a rigorously systematic manner by carrying out computer simulations, by utilizing also data obtained in previous papers. The following points were discussed in detail: (1) relationships among initial polymer concentration ν, fraction size ϱ and volume ratio of the polymer‐lean phase to the polymer‐rich phase R, (2) parameter responsible for fractionation efficiency, (3) upper limit of ν attainable for a given fractionation run, and (4) total volume of solvent necessary to separate a fraction having a given polydispersity. It was fully confirmed that SSF is preferable to or at least equivalent with SPF in any respect and that very narrow fractions can be obtained by single SSF.
Modelle für die Durchdringung von Knäuelmolekülen aus Lichtstreuungsmessungen
Authors: Oberthür Radulf Christoph
Published: April 2003

Aus der Konzentrationsabhängigkeit der Streustrahlung gelöster Makromoleküle läβt sich ein Parameter extrapolieren, der Wechselwirkungsradius genannt wird. Er steht zum ausgeschlossenen Volumen in einem ähnlichen Verhältnis wie der Trägheitsradius zur Masse eines Teilchens.

Lichtstreuungsmessungen an Polystyrol der Uneinheitlichkeit U =0,05, gelöst in Toluol bei 25°C ergeben bei einer Molmasse von 2,95.106 g/mol und einem Trägheitsradius von 900Å für das ausgeschlossene Volumen 6,4.109Å3 und für den Wechselwirkungsradius 1230Å. Damit lassen sich Paarverteilungsfunktionen ausschließen, die durchaus in Einklang mit dem Wert für das ausgeschlossene Volumen stehen, so z. B. die, die einem undurchdringlichen Knäuelkern entsprechen. Vielmehr werden Paarverteilungsfunktionen wahrscheinlich gemacht, wo einer zunehmenden Durchdringung ein langsam wachsender Widerstand entgegen gesetzt wird. Eine weitgehende gegenseitige Durchdringung ist weniger wahrscheinlich, wird aber anscheinend nicht vollständig verhindert.
Über die kinetik des thermischen und thermooxidativen abbaus von polyäthylenterephthalat
Authors: Bîrlădeanu Constantin , Vasile Cornelia , Schneider Ioan‐Adam
Published: April 2003

Es wurden die scheinbaren kinetischen Parameter der thermischen und thermooxidativen Abbaureaktionen von Polyäthylenterephthalat für nicht‐isotherme Bedingungen bestimmt und die Abhängigkeit dieser Werte von der Aufheizgeschwindigkeit, dem mittleren Molekulargewicht und vom Umsatzgrad festgestellt. Es wurde gefunden, daß der Abbau in Stickstoff nach einem einheitlichen Kettenmechanismus mit kurzen kinetischen Ketten erfolgt, wogegen sich in Luft der Kettenabbaureaktion Oxidationsprozesse überlagern, bemerkbar an einem exothermen Ausschlag der DTA‐Kurven.
Cristallisation du poly(oxyéthylène) dans des copolymères biséquencés, 1. Étude dilatométrique
Authors: Seow Pin Kwong , Antione Skoulios Yves Gallot
Published: April 2003

On a étudié au moyen de la dilatométrie la cristallisation directe à partir de l'état fondu et le recuit des séquences poly(oxyéthylène) d'une série copolymères biséquencés poly(méthacrylate d'éthyle)/poly(oxyéthylène) et polystyrène/poly(oxyéthylène). On a montré que les taux de cristallinité atteints sont élevés. On a calculé le volume spécifique partiel de chacune des séquences. On a étudié enfin la fusion des séquences cristallisées.
Photosensitized polymerization of vinyl acetate under high pressure
Authors: Yokawa Masaru , Ogo Yoshiaki
Published: April 2003

By use of the rotating sector technique under high pressure, the changes which occur in the rate constants of the propagation and the termination reactions in the polymerization of vinyl acetate, photosensitized with azocyclohexane‐1,1′‐dicarbonitrile were studied at 30°C over a pressure range of 1 to 1000 bar. The effects of pressure on the individual rate constants were determined and the activation volumes of propagation and termination were obtained as −24,0 and 16,3 cm3 mol−1, respectively.

The effect of pressure on the propagation reaction of vinyl acetate was somewhat larger than those of styrene and methyl methacrylate, and the termination rate constant showed a smaller decrease with pressure than those of the other vinyl monomers, especially of methyl methacrylate. The problem concerning the differences of the pressure effect on the termination reaction is discussed from the view point of the chain transfer reaction to monomer.
Experimental verification of modern theory of molecular weight fractionation based on solubility difference
Authors: Kamide Kenji , Miyazaki Yukio , Abe Tatsuyuki
Published: April 2003

An attempt was made to verify the modern theory of molecular weight fractionation based on solubility behavior by experiment. Atactic polystyrene (PS) in methylcyclohexane (MCH) and in cyclohexane (CH) were employed for this purpose. The following quantities were determined experimentally and compared with theoretical values calculated with the aid of an electronic computer: The partition coefficient σ, volume ratio of polymer‐lean phase to polymer‐rich phase R, polymer volume fraction in the two phases, vp(1) and vp(2), weight‐average molecular weight M̄w and the breadth of the molecular weight distribution (the ratio of weight‐ to number‐average molecular weight, M̄w/M̄n and standard deviation σ′) of the polymers in both phases. The experimental data can be well explained in terms of theory if the concentration dependence of the polymer/solvent interaction parameter χ, expressed by p, is reasonably taken into account, i.e., p = 0,7 for PS in MCH and p = 0,6 for PS in CH. It was shown that σ depends slightly on molecular weight.
A theoretical study on the proton chemical shifts of polypropylene
Authors: Asakura Tetsuo , Ando Isao , Nishioka Atsuo
Published: April 2003

The proton chemical shifts of dyad, triad, and tetrad protons in an isolated chain of polypropylene were calculated, taking into account its configurations and conformations using Pople's approximation.

The calculations were carried out as functions of four parameters, i.e., a, Δψ, ω, and fr: a represents the ratio of the magnetic anisotropy of the CHCH3 bond to that of the CHCH2 bond, Δψ the deviation for the rotational angle, ω the statistical weight corresponding to the four‐bond interaction, and fr the amount of the racemic units contained in a chain. By introducing the parameter, a, the observed orders of dyad and triad protons were well explained and the value of a was in the range of about 1,10 to 1,25. However, the agreement between the observed and calculated results was insufficient with respect to the large difference between syn and anti protons and the order of tetrad protons. Here, a priori probabilities of specified conformations necessary to the estimation of the chemical shift were calculated using Flory's matrix method. These results were compared with the conformation of polypropylene obtained by Flory et al. and Zambelli et al.
Zum mechanismus der radiolyse von 3,4‐polyisopren
Authors: Kaufmann Rudolf , Heusinger Helmut
Published: April 2003

Zur Beschreibung der strahleninduzierten Veränderungen in 3,4‐Polyisopren wurde die Ausbildung von Kettenvernetzungen über Sol‐Gel‐Analysen (G‐Wert der Kettenver‐netzung, G(cl)≈2) und die Abnahme der Doppelbindungen mittels IR‐Spektroskopie (G(−3,4)≈120) bestimmt. Weiterhin wurde die Abhängigkeit der Doppelbindungsabnahme von der Dosisleistung und der Temperatur untersucht (Dosisleistungsexponent = 0,9, Aktivierungsenergie = 11,7 kJ/mol). Durch Zugabe des Radikalfängers Anthracen wird die Doppelbindungsabnahme nicht beeinflußt, während die Ausbildung von Vernetzungen stark vermindert wird.

Aufbauend auf diese Ergebnisse, unter Berücksichtigung der ESR‐spektroskopisch nachgewiesenen Radikale, wird ein Mechanismus diskutiert, bei dem das durch ionisierende Strahlung erzeugte Radikalkation einerseits radikalisch eine Vernetzung bildet und andererseits eine kationische Kettenreaktion startet, die zu Cyclisierungen führt. Der im Polymeren neben der Vernetzung in geringem Maße auftretende Kettenbruch wird mit dem Gehalt an 1,4‐Einheiten in Zusammenhang gebracht.
Untersuchungen zu den orientierungs‐ und dichtefluktuationen in amorphen polymeren mit hilfe der lichtstreuung
Authors: Dettenmaier Manfred , Fischer Erhard W.
Published: April 2003

Es wurden mit einem Lichtstreuphotometer die Orientierungs‐ und Dichtefluktuationen in den amorphen Polymeren «Polycarbonat» (Poly(oxycarbonyloxy‐1,4‐phenylenisopropyliden‐1,4‐phenylen)) und Polystyrol in Abhängigkeit von der Temperatur untersucht. Ferner führten wir ergänzende Messungen an Oligomeren des Polystyrols und an der flüssig‐kristallinen Verbindung 4‐Butyl‐N‐(p‐methoxybenzyliden)anilin (MBBA) in der isotropen Phase durch.

Aus der Höhe der depolarisierten Lichtstreuung ergab sich, daß eine Orientierungskorrelation, wie sie für einige Bündelmodelle vorgeschlagen wurde, nicht auftritt. Besonders detaillierte Aussagen konnten für Polystyrol gemacht werden. Die depolarisierte Lichtstreuung war im gesamten Winkelbereich konstant und von der Temperatur unabhängig. Die Anisotropie pro Monomereinheit der Oligomeren hat bereits eine ähnliche Größe wie die des Polymeren, d. h. im Polymeren liegen keine zusätzlichen Orientierungsfluktuationen vor. Die Orientierungskorrelation der Monomereinheiten im Polymeren konnte vollständig auf die in Knäueln vorhandene zurückgeführt werden.

Die Höhe und Temperaturabhängigkeit der durch Dichtefluktuationen verursachten Lichtstreuung des Polystyrols stimmten mit den Ergebnissen der Fluktuationstheorie überein. Es fand somit keine Streuung an Dichtefluktuationen spezifisch makromolekularer Art statt.
Estergruppenhaltige Polyalkenylene durch Olefin‐Metathese
Authors: Ast Wolfgang , Rheinwald Günter , Kerber Robert
Published: April 2003

Die ringöffnende Polymerisation von Estergruppen‐substituierten Cycloolefinen in Gegenwart geeigneter Metathese‐Katalysatoren wie WCl6/(CH3)4Sn führt zu linearen Polyalkenylenen mit seitenständigen Estergruppen. Die Ausgangsmonomeren 9‐Äthoxycarbonyl‐bicyclo[6.1.0]non‐cis‐4‐en (3), 13‐Äthoxycarbonyl‐bicyclo[10.1.0]trideca‐trans‐4, trans‐8‐dien (5) und 3‐Äthoxycarbonyl‐tricyclo[3.2.1.02,4]oct‐6‐en (7) werden über eine Carbenreaktion mit Diazoessigsäureäthylester aus den Cycloolefinen cis‐1, cis‐5‐Cyclooctadien (2), cis‐1, trans‐5, trans‐9‐Cyclododecatrien (4) und Norbornadien (6) erhalten. Die entsprechenden Polyalkenylene (3a, 5a sowie 7a) besitzen relativ hohe Molekularge‐wichte. Ihre Konstitution wird spektroskopisch und durch gaschromatographische Analyse der Abbauprodukte nach Olefin‐Metathese mit einem niedermolekularen Olefin (4‐Octen) bestimmt.
Comparative investigation of short‐range order in unbranched alkanes and polyethylene
Authors: Ovchinnikov Yuri K. , Antipov Eugenie M. , Markova Galina S. , Bakeev Nikolie F.
Published: April 2003

This paper presents basic results obtained in the X‐ray investigation of liquid unbranched alkanes of type CnH2n+2 and polyethylen (PE) melts of molecular weights from 86 (hexane) to 2.106 (PE) in the temperature range from 0to 350°C. The position of the maximum of the X‐ray scattering curve 2θmax, and the half‐width Δ1/2 of the amorphous halo, with average errors of ±1,5′ and ±6′, respectively were measured.

The experimental results were used for a comparative analysis of short‐range ordering in polyethylene melts and their low‐molecular analogues. The thermal expansion coefficients of the liquids and their “X‐ray densities” were calculated (assuming that the packing is hexagonal). The analytical dependences on the molecular weight for the melting and boiling point 2θ = f(M) and 2θ = f(M) were derived, and a “critical molecular weight” was calculated for the transition from oligomer to polymer. The data revealed jump‐wise changes of the short‐range order parameters in unbranched alkanes with lower number of carbon atoms in passing from an odd to the next even homologue, which indicates a high degree of ordering in the liquid.
Depolarization thermocurrent and dielectric study in polyethylene
Authors: Berticat Philippe , Ai Bui , Giam Hoang The , Chatain Daniel , Lacabanne Colette
Published: April 2003

Our aim is to correlate dielectric relaxation with structure of polyethylene. By using the depolarization thermocurrent (DTC) technique it is shown that the so‐called α‐, β‐, γ‐relaxation modes have a fine structure. The “elementray” processes have been isolated experimentally; they are well described by the assumption of thermally activated relaxations. The data deduced from the analysis of the resolved DTC spectra allow to calculate the complex dielectric constant versus temperature and frequency. The calculated dielectric loss curves versus temperature are found in good agreement with bridge experiments performed on the same samples, in the available frequency range.
Extended‐chain crystals of POM‐copolymers: Synthesis, structure and properties
Authors: Dröscher Michael , Hertwig Klaus , Reimann Horst , Wegner Gerhard
Published: April 2003

The synthesis of extended chain crystals of copolymers of trioxane and 1,3‐dioxolane, 1,3‐dioxane, 1,3‐dioxepane, and 1,3,6‐trioxocane by cationic copolymerization is described. Density, melting point, and enthalpy of melting are reported as depending on the mole fraction x2 of the comonomer units. In each series the density decreases linearly with increasing comonomer content for x2 < 0,1. The melting temperature Tm decreases first linearly with increasing x2, but reaches a plateau in which Tm becomes independent of the composition. The data are analysed in terms of Eby's theory of melting behaviour, and defect enthalpies related to the individual comonomer units are derived.
Über das auftreten von verzweigungsreaktionen bei der copolymerisation von trioxan mit 1,3‐dioxolan
Authors: Sextro Günter , Burg Karlheinz , Cherdron Harald
Published: April 2003

Bei der Homopolymerisation von Trioxan kann prinzipiell mit dem Entstehen von verzweigten Molekülen gerechnet werden. Der Nachweis verzweigter Strukturen gestaltet sich angesichts der thermischen Instabilität von Trioxan‐Homopolymeren besonders schwierig; günstigere Verhältnisse liegen bei Trioxan‐Copolymeren vor.

Aufgrund von vergleichenden Sphärolithgrößenuntersuchungen und verschiedenartigen Abbauversuchen an Trioxan‐Copolymeren, ‐Blockcopolymeren und‐Terpolymeren haben wir erste experimentelle Hinweise für das Auftreten von Verzweigungsreaktionen an Oxymethylen‐und an Oxyäthylengruppen während der Polymerisation erhalten. In einem ersten Schritt erfolgt eine Hydridübertragung unter Bildung eines neuen kationischen Zentrums, in einem zweiten Schritt folgen Spaltungs‐ oder Verzweigungsreaktion.

Bei der Copolymerisation von Trioxan mit 1,3‐Dioxolan überwiegt die Spaltungsreaktion, insbesondere bei hohen Polymerisationstemperaturen, während bei Blockcopolymeren aus Trioxan/1,3‐Dioxolan und Polyglykol Hydridübertragungen an der Polyoxyäthylenkette bevorzugt zu Verzweigungsreaktionen führen.
Schlangenkäfig‐polymere, 1. Darstellung verschiedener schlangenkäfig‐polyelektrolyte auf der basis von polyacrylamiden und einem anionenaustauscher
Authors: Kaczmar B. Ulrich , Traser Sigrid
Published: April 2003

Aus α‐, β‐ und γ‐Aminosäuren und Acryloylchlorid wurde eine Reihe von Monomeren mit sauren Gruppen erhalten. Ihre Einführung in einen stark basischen, makroporösen Anionenaustauscher (Lewatit®) und anschließende Polymerisation führte zu Schlangenkäfig‐Polyelektrolyten, die durch die restliche Anionenaustauschkapazität, die neuentstandene Kationenaustauschkapazität und die Menge an immobilisierten Grundbausteinen charakterisiert wurden.
Vinyl monomer complexes in copolymerization processes. Studies on the complexes of acrylonitrile and methyl methacrylate with lewis acids
Authors: Kuran Witold , Pasynkiewicz Stanisław , Florjanczyk Zbigniew , Lusztyk Ewa
Published: April 2003

Complexes of acrylonitrile and of methyl methacrylate with various Lewis acids, 1 and 2, were studied by means of IR, NMR, and UV spectroscopy. The influence of the Lewis acid strength on the induction effect and on the delocalization of π‐electrons in the complexed monomer molecule was established. As the relative acidity of the complexing agent is increased, the inductive effect of the nitrile or of the carbonyl group in the complex molecule rises, whereby the electron density on the carbon atom in β‐position in the vinyl group diminishes. Complexation of the monomer also results in increased delocalization of π‐electrons in the molecule. In the complexes with moderately strong Lewis acids like CH3AlCl2 and C2H5AlCl2, delocalization of π‐electrons seems to reach its maximum. The methyl methacrylate‐C2H5AlCl2 complex was found to give a charge‐transfer complex with 1,5‐cyclooctadiene. On the basis of the present spectroscopic studies and of earlier studies on copolymerization of acryl monomers with butadiene, the delocalization of π‐electrons in the complexed monomer molecule is believed to be one of the major factors controlling the rate of copolymerization.
Catalysis of olefin transformation by tungsten complexes, 5. Tungsten carbonyl carbenes activated by titanium tetrahalides as catalysts for the ring‐opening polymerization of cyclopentene
Authors: Chauvin Yves , Commereuc Dominique , Cruypelinck Daniel
Published: April 2003

The reaction of TiCl4 with tungsten carbonyl carbene derivatives such as (CO)5W‐[C(OEt)R] affords catalysts which display a very high activity for the “methathetic” polymerization of cyclopentene. Thus, the equilibrium concentration of cyclopentene can be reached with a cyclopentene: W mole ratio of 106:1. The formation of the active species is thermally or photochemically assisted. A large excess of TiCl4 is needed during the polymerization process.