bluuebunny/crossref_metadata_2025_split huggingface dataset:
Über die struktur der polyketone aus äthylen und kohlenmonoxid
Authors: Hoyer Herbert , Fitzky Hans‐Georg 
Published: April 2003

AbstractDie Copolymerisation von Äthylen und Kohlenmonoxid vollzieht sich nicht nach einem einheitlichen Mechanismus. Außer zum dominierenden linearen Einbau des Äthylens in die entstehenden Polyketonmoleküle kommt es auch in geringer Menge zur Kettenverzweigung durch querständigen Einbau des Äthylens. Dadurch entstehen 1.3‐Diketon‐Gruppie‐rungen, die nach Enolisierung und Umsetzung mit Kupferoleat Kupferkomplexe bilden können. Die komplexe Bindung von Kupferionen in einem Polyketon wird durch Elektronenspinresonanzspektroskopie bewiesen. Wegen der Spezifität der Elektronenspinresonanzspektren stören andersartige Kupferionen diesen Nachweis nicht.Kupferkomplexe, die bei der Reaktion von Kupferoleat mit einem Polyketon entstehen, entsprechen den Komplexen der Enolformen niedrigmolekularer 1.3‐Diketone nicht vollständig. In den Komplexen des Polyketons nimmt nur eine enolisierte Gruppe an der Komplexbildung teil, im Kupfersalz des Acetylacetons dagegen zwei. Die Komplexbindung im Kohlenmonoxid‐Äthylen‐Copolymeren ist vermutlich sterisch erschwert, so daß das eingebaute Kupferion einem gemischten Komplex zugehört, an dem sich als Liganden außer einer enolischen Gruppe auch eine oder zwei Carboxylgruppen des zum Kupferaustausch eingesetzten Kupferoleats beteiligen.
Vinyl polymerization. 288. Polymerization of vinyl monomers photosensitized by 3‐acetoxy‐3.5.5‐trimethyl‐1‐pyrazoline
Authors: Nakaya Tadao , Ikeda Hisayoshi , Imoto Minoru 
Published: April 2003

AbstractThe photopolymerization of vinyl monomers (e. g., methyl methacrylate and styrene) in benzene solution can be sensitized by 3‐acetoxy‐3.5.5‐trimethyl‐l‐pyrazoline (ATP). The kinetics of the photopolymerization was investigated in the case of methylmethacrylate (MMA). The rate of polymerization was found to be proportional to the one half power of the ATP concentration and approximately to the first power of the MMA concentration. The chain‐transfer constant of ATP for MMA under UV irradiation was estimated as 0.0 at 30°C. The plausible mechanism proposed for the overall reaction is discussed in the light of the experimental results.
The unit cell of poly‐p‐xylylene and the structure of solution‐grown crystals
Authors: Kubo Shigeo , Wunderlich Bernhard 
Published: April 2003

AbstractA further refined unit cell of alpha poly‐p‐xylylene is proposed. It is monoclinic with the parameter a = 5.92, b = 10.64, c (chain axis) = 6.55 Å, and β = 134.7°. Darkfield electron microscopic observation of solution‐grown lamellae revealed a tent‐like shape of the lamellae. A possible packing of the chains in the crystal is given.
A nuclear magnetic resonance study on the adsorption of poly(methyl methacrylate) at a solid/liquid interface
Authors: Miyamoto T. , Cantow H.‐J. 
Published: April 2003

AbstractThe adsorption and desorption behaviour of tactic poly(methylmethacrylate) (PMMA) chain on silica gel from chloroform solution are investigated by using high‐resolution NMR spectroscopy.The conformation of PMMA chains adsorbed on silica and the effects of polar additives on polymer adsorption are discussed.It is shown that the adsorption of PMMA on silica surface is so strong as to restrict highly the polymeric motion of PMMA at segmental level. The conformation of PMMA adsorbed on silica gel surface is considered to be a uniformly adsorbed and relatively compressed form. The NMR technique is very effective to estimate the fraction of segments of which the segmental motion is restricted because of the adsorption on silica gel.The methanol/silica interaction is stronger than the PMMA/silica interaction, and methanol reduces rapidly PMMA adsorption on silica. The rate of adsorption displacement of PMMA by methanol is relatively rapid and PMMA almost reaches the equilibrium adsorption value within 30 min at room temperature.
Thermal degradation of copolymers of methyl methacrylate and n‐butyl acrylate. I. Thermal analysis
Authors: Grassie N. , Fortune J. D. 
Published: April 2003

AbstractBy means of thermal volatilisation analysis (TVA) the principal features of the thermal degradation of a series of copolymers of methyl methacrylate and n‐butyl acrylate covering the entire composition range have been revealed. The degradation which is initiated in poly(methyl methacrylate) at unsaturated chain terminal structures is progressively suppressed by increasing concentrations of copolymerised n‐butyl acrylate while the degradation initiated by random chain scission moves to higher temperatures. It is clear from the TVA thermograms that the products of degradation consist of a complex mixture of gases and liquids and a viscous oily fraction. Energies of activation have been derived from thermal gravimetric analysis thermograms by the method of COATS and REDFERN. The increase with increasing n‐butyl acrylate content of the copolymer has been associated with the greater heat of polymerisation of n‐butyl acrylate compared with methyl methacrylate.
Diimide as a reagent for the hydrogenation of unsaturated polymers
Authors: Harwood H. James , Russell David B. , Verthe John J. A. , Zymonas Joseph 
Published: April 2003

AbstractThe hydrogenation of various butadiene polymers and of polyisoprene with diimide generated in situ from p‐toluenesulfonylhydrazide was investigated. The best results were obtained when concentrated polymer solutions were heated with a five‐fold excess of p‐toluenesulfonylhydrazide. Complete hydrogenation of all polymers was obtained under such conditions, but some 1,2‐butadienyl units were found to contain fragments derived from p‐toluenesulfonylhydrazide. Diimide seems to be a good reagent for hydrogenating unsaturated units in polymers, but mild conditions for generating it are needed if side reactions are to be avoided.
On the polymerization of vinyl‐ and ethynylferrocene
Authors: Simionescu Cr. , Lixandru T. , Negulescu I. , Mazilu I. , Tătaru L. 
Published: April 2003

AbstractThe present paper deals with the polymerization of vinylferrocene and ethynylferrocene in the presence of some initiators or catalysts used for the polymerization of classical vinyl and ethynyl monomers. Ethynylferrocene was polymerized with lauroyl peroxide and B(iso‐C3H7)3 as radical initiators and with substituted phosphine‐transition metal complexes as catalysts, a reaction mechanism being proposed for the last case. Vinylferrocene was polymerized with soluble ZIEGLER systems, e.g., AlEt2Cl/Cu(C5H7O2)2. Attempts to polymerize vinylferrocene with phosphine complexes and ethynylferrocene with soluble ZIEGLER catalyst, Al(iso‐C4H9)3/VO(C5H7O2)2, were unsuccesfully. However, vinylferrocene unlike ethynylferrocene was polymerized with good yields in the presence of the system [–P(C6H5)2]2·Ni(C5H7O2)2.The polymers obtained were investigated with respect to their thermal and electrical properties.
High pressure copolymerization of cyclopentene with maleic anhydride
Authors: Yokawa Masaru , Ogo Yoshiaki , Imoto Tatsuya 
Published: April 2003

AbstractRadical copolymerization of cyclopentene with maleic anhydride was investigated under high pressure up to 6000 kg/cm2 at 60°C.The rate of copolymerization increased markedly with pressure and the conversion at 6000 kg/cm2 attained a maximum constant value in a few minutes. This behavior indicated very large absolute values for the activation volume compared with other vinyl polymerization systems.The copolymer composition was affected by pressure, for a given monomer feed the content of cyclopentene in the copolymer increased with pressure. This is an explanation for the penultimate effect due to cyclopentene. High pressure is presumed to be effective for eliminating the penultimate effect in copolymerization.
Copolymere aus Vinylhalogeniden und olefinen. II. Quantitative IR‐spektroskopische untersuchungen an Vinylchlorid/Isobuten‐Copolymeren
Authors: Brück Dieter , Hummel Dieter O. 
Published: April 2003

AbstractZur Identifizierung sequenzempfindlicher Banden in den IR‐Spektren der Vinylchlorid/Isobuten‐Copolymeren wurden die überlagerten δ(CH2)‐ und δ(CH3)‐ (1500–1350 cm−1), ρ(CH2)‐ (1000–850 cm−1) und ν(CCl)‐Schwingungen (730–600 cm−1) in Einzelbanden zerlegt. Die Halbwertsbreiten und die relativen integralen Extinktionen dieser Banden wurden an einer Copolymerreihe in Abhängigkeit von der Zusammensetzung der Copolymeren bestimmt. Die Polymerisationstemperatur betrug 23°C.
Copolymere aus Vinylhalogeniden und olefinen. IV. Kernresonanzspektroskopische untersuchungen an Vinylchlorid/Isobuten‐Copolymeren
Authors: Brück Dieter , Hummel Dieter O. 
Published: April 2003

AbstractIn dieser Arbeit wird für eine von Reihe von strahlenchemisch hergestellten Hochpolymeren aus Vinylchlorid (VC) und Isobuten (IB) die Bruttozusammensetzung und die Häufigkeit der in ihnen enthaltenen, kompositiv und konfigurativ unterschiedlichen Sequenzen durch bochauflösende protonenmagnetische Resonanz bei 220 MHz ermittelt.Die durch Vergleich der Flächen unter den Methyl‐ und Methinresonanzen errechneten Copolymerisationsparameter (rA = 2,28 ± 0,13, rB = 0,13 ± 0,03) ermöglichen mit Hilfe der Kinetik der Copolymerisation eine Vorausberechnung der kompositiven Primärstruktur.Der Bereich der Methinresonanz wurde in sechs Peaks zerlegt, die zu den sechs möglichen, durch die Kernresonanz unterscheidbaren Triaden mit zentraler VC‐Einheit gehören. Der Vergleich der berechneten mit den gemessenen Triaden erlaubte eine Zuordnung zu den im Hinblick auf ihren kompositiven und konfigurativen Aufbau verschiedenen Triaden. Der hierfür erforderliche,, Taxiparameter σ ließ sich aus dem Spektrum des PVC ableiten. Das für die Berechnung der Copolymerisationsparameter und für die Ermittlung der Zuordnung vorausgesetzte Copolymerisationsmodell und der Parameter σ wurden mit Hilfe der gemessenen relativen Triadenhäufigkeiten auf ihre Gültigkeit hin geprüft.
Radical reactions initiated by chelate complexes of transition metals. IX. Catalytic decomposition of benzoylperoxide and transfer reactions of free radicals to (−)‐ephedrine
Authors: Bartoň J. , Tiňo J. , Horanská V. 
Published: April 2003

AbstractThe kinetics and mechanism of catalyzed decomposition of benzoyl peroxide in benzene in the presence of bis‐(−)‐ephedrine copper(II) chelate (Cueph) and free ligand i.e. (−)‐ephedrine were studied. The kinetics of benzoyl peroxide (BPO) decomposition in its initial stage may be described by the equation:

The activation energy of this reaction is 10 kcal/mole. During the decomposition of benzoylperoxide in the presence of bis‐(−)‐ephedrine copper(II) chelate a decay of paramagnetic Cu2⊕ particles occurs, the activation energy of this process being 9.1 kcal/mole. By transfer reactions of the radicals generated by the decomposition of benzoyl peroxide with ligand (−)‐ephedrine, free radicals are formed with the unpaired spin localized at the nitrogen atom. The identification of these radicals has been accomplished by comparing the experimental ESR spectra to calculated and simulated ones.
NMR investigations of molecular motion in synthetic polyisoprenes at liquid helium temperatures
Authors: Svoboda J. , Odehnal M. 
Published: April 2003

AbstractThe behaviour of the molecular motion in synthetic cis‐ and trans‐1,4‐polyisoprenes was studied by nuclear magnetic resonance. The line‐widths (ΔHpp), second (M2) and fourth moments (M4) of the absorption curves were measured at 77, 4.2, and 1.3 K. The obtained values of ΔHpp and M2 for cis‐polyisoprene indicate that the molecular motions are apparently not completely quenched at 77 K since there is a further increase in the values of M2 and ΔHpp when decreasing the temperature from 77 to 4.2 K. It was found also that the value of M2 at 4.2 and 1.3 K (≅ 20 G2) was larger than the previously computed one for a rigid lattice (18.5 G2). The temperature dependence of M2 and ΔHpp for trans‐polyisoprene is different from that for cis‐polyisoprene. The values of M2 are constant in the range from 77 to 1.3 K (≅ 19.5 G2), which suggests that the molecular motion is presumably stopped in this polymer already at 77 K.
Formation of quinone methide in the self‐cure of quinoid phenol formaldehyde resin
Authors: Yoshikawa Toshio , Kumanotani Ju 
Published: April 2003

AbstractThe study of the reaction of some methylenebisphenols with chloranil in ethanol and also of a phenol formaldehyde condensate prepared by acid catalysis, reveals that quinone methide is formed in the self‐cure of quinoid phenol formaldehyde resin. The quinone methide reacts with ethanol to give an adduct. The structure of the alcohol adduct is identified by NMR and IR data and by means of pyrolysis.
On the mechanism of chain propagation in radiation‐induced polymerizations of trioxane in the solid state
Authors: Jaacks V. , Boehlke K. , Kern W. 
Published: April 2003

AbstractThe mechanism of radiation‐induced polymerizations in the solid state has been a subject mostly open to speculation. As radiation usually generates several kinds of active species (radicals and ions) it is difficult to find out, which of these actually causes polymerization.We have developped a method distinguishing between cationic and anionic active centers. Cationic polymerizations are terminated by addition of a base such as sodium alkoxide in a suitable solvent. The alkoxide is incorporated into the polymer as an endgroup. This endgroup is determined analytically after isolation and purification of the polymer. The incorporation of alkoxy endgroups into the polymer is a proof of the occurrence of polymer chains with cationic chain ends. It was shown by this method that crystalline trioxane, polymerized by γ‐rays at 60°C, contains polyoxymethylene cations. It is assumed that with these cationic active centers propagation is similar to polymerizations initiated by LEWIS acids.
Anionic chain ends can be detected by an analogous way. Polymerizations are terminated by addition of excess alkyl iodide which produces alkoxy endgroups from the anionic chain ends. Surprisingly, in the radiation‐induced polymerization of crystalline trioxane some anionic chain ends were also found in the polymer. It is assumed that these anions do not propagate and that they are only counter‐ions of the propagating cationic chain ends.
Photopolymerization of methyl methacrylate induced by thiocyanogen or by pyridinium thiocyanate
Authors: Nishihara Koji , Sakota Naokazu 
Published: April 2003

AbstractThe photopolymerization of methyl methacrylate (MMA) in the presence of thiocyanogen ((SCN)2) or pyridinium thiocyanate (PySCN) was kinetically studied. The initial rate of photopolymerization (Rp) with (SCN)2 in benzene or acetic acid at 35 ± 0.5°C was shown to be

Under the experimental conditions chosen (SCN)2 shows a first order photochemical decomposition with a rate constant of (1.4 ± 0.05). 10minus;3 secminus;1 as estimated from the kinetic data. The standstill of the polymerization at a low conversion, the inhibition of polymerization by hydroquinone and the free radical type composition curve of the copolymerization of MMA and styrene indicate the polymerization of MMA with (SCN)2 to be a dead‐end polymerization based on a free radical mechanism.
On the other hand the overall rate of photopolymerization of MMA with PySCN in dimethylformamide at 35 ± 0.5°C is described by the equation:

Conversion vs. time plots of the polymerization with PySCN are straight lines up to relatively high conversions which pass the origin, and the polymerization is not inhibited by dimethylformamide but by hydroquinone. These results show that the photopolymerization with PySCN is not a dead‐end polymerization and proceeds also via a radical mechanism which involves the participation of monomer in the initiation step.
Electrochemically initiated cationic polymerization of trioxane in benzonitrile and nitrobenzene. Part II
Authors: Mengoli Giuliano , Vidotto Graziano 
Published: April 2003

AbstractElectrochemically initiated cationic polymerizations of trioxane in benzonitrile and in nitrobenzene have been carried out. In both of these solvents the polymerizations go on even when the current is switched off. In benzonitrile the polymerizations are affected, however, by a slow termination reaction probably involving the solvent. This leads to a satisfactory thermal stability of the polyoxymethylenes. Based on certain assumptions the specific propagation rate constants of trioxane polymerizations in both solvents and the corresponding activation energies have been deduced from the initial polymerization rates of experiments carried out at various concentrations of initiating species and at various temperatures.
Polymerization of methyl acrylate in aqueous cationic soap solutions
Authors: Morris Carolyn E. M. , Parts Adolf Gustav 
Published: April 2003

AbstractThe polymerization of methyl acrylate in aqueous cationic soap solutions has been examined. The rate of polymerization was found to pass through a minimum with increasing soap concentration. The inhibition period increases considerably with increase in soap concentration. The charge on the latex particles was changed from negative to positive.The latexes of low charge were quite unstable and these systems showed the slowest rate of polymerization. Either the polymerization rate constant in solution is considerably higher than in bulk, or the decomposition of peroxydisulphate in the presence of monomer is increased. Transfer reactions play an important rǒle in the polymerization.
Caractérisation de réactions primaires de dégradation oxydante au cours de l'autoxydation des polyoxyéthylènes à 25 °C: Étude en solution aqueuse avec amorçage par radiolyse du solvant. I. Étude viscosimétrique: Stabilité des hydroperoxydes du polyoxyéthylène et cinétique de production des coupures
Authors: Crouzet Claude , Marchal Jean 
Published: April 2003

AbstractL'autoxydation du polyoxyéthyène en solution aqueuse à 25°C a été realisee en amorçant les réactions par les radicaux HO• provenant de la radiolyse du solvant. Les expériences montrent que l'hydroperoxydation du polymère est accompagnée d'une dégradation oxydante. La cinétique de production des coupures montre que cette degradation oxydante doit être expliquée par des réactions primaires obéissant à un mécanisme de réactions en chaînes. L'étude de I'effet prolongé a confirmé que la production de coupures par décomposition des hydroperoxydes est négligeable dans les conditions où l'autoxydation du polymère a été réalisée.
Caractérisation de réactions primaires de dégradation oxydante au cours de l'autoxydation des polyoxyéthylènes à 25°C: Étude en solution aqueuse avec amorçage par radiolyse du solvant. III. Mécanisme monomoléculaire de décomposition des radicaux peroxyles et schéma cinétique de la production des coupures observées par viscosimétrie
Authors: Crouzet Claude , Marchal Jean 
Published: April 2003

AbstractLes coupures statistiques observées sans période d'induction au cours de I'autoxydation du polyoxyéthylène en solution aqueuse, à 25°C et à I'abri de la lumière, sont expliquées par une réaction monomoléculaire de décomposition des radicaux peroxyles secondaires formés sur le polymère. Le schéma cinétique de I'autoxydation du polyoxyéthylène construit avec cette réaction rend bien compte de la cinétique experimentale de la dégradation oxydante de ce polymère.
Caractérisation de réactions primaires de dégradation oxydante au cours de l'autoxydation des polyoxyéthylènes à 25°C: Étude en solution aqueuse avec amorçage par radiolyse du solvant. V. Triéthylèneglycol: Produits d'oxydation et schéma cinétique
Authors: Decker Christian , Marchal Jean 
Published: April 2003

AbstractAu cours de l'autoxydation radio‐induite à 25°C du triéthylèneglycol en solution aqueuse, la formation de onze produits primaires de dégradation a été observée sà côté de celle des hydroperoxydes. Les réactions proposées précédemment pour l'autoxydation du diéthylèneglycol restent valables. II faut les compléter par des reactions de propagation intramoléculaires par des radicaux peroxyles et alcoxyles rendues possibles par la longueur des molécules de triéthylèneglycol.
Caractérisation de réactions primaires de dégradation oxydante au cours de l'autoxydation des polyoxyéthylènes à 25°C: Étude en solution aqueuse avec amorçage par radiolyse du solvant. VI. Polyoxyéthylène: Produits d'oxydation et schéma cinétique
Authors: Decker Christian , Marchal Jean 
Published: April 2003

AbstractL'autoxydation du polyoxyéthylène en solution aqueuse a été réalisée par amorçage radiochimique à 25°C. L'hydroperoxydation du polymére est accompagnèe par une dégradation oxydante produisant du formaldéhyde et neuf autres composés primaires de bas poids molèculaire. Les rèsultats sont expliquès par la décomposition monomoléculaire de radicaux peroxyles secondaires PO•2, selon un mécanisme à six centres avec libération de radicaux alcoxyles PO•, et par des réactions de propagation intramoléculaires à courte distance par les deux types de radicaux libres PO•2 et PO•.
Dilute solution properties of trans polypentenamer: [η]—M relations and molecular conformations
Authors: Gianotti G. , Bonicelli U. , Borghi D. 
Published: April 2003

AbstractInvestigations have been accomplished on the solution properties of polypentenamer samples with a content of about 80% of trans units.Some fractions with a low degree of polydispersity were characterized by viscosimetric, osmotic and light scattering methods.Relations [η]—M in toluene and cyclohexane at 30°C and in the pseudo‐ideal solvent, isoamyl acetate at 38°C, were obtained. They allow to calculate the conformational parameters of the macromolecule in the unperturbed state. The data obtained both from a pseudo‐ideal and from good solvents are discussed.
Zur kenntnis der amylose der kartoffelstärke. 2. Mitt.
Authors: Seidemann Johannes 
Published: April 2003

AbstractDie mit Amylose bezeichnete Gruppe von Kohlenhydraten der Stärke erweist sich nach verschiedenen Richtungen hin als heterogen. Durch die papierchromatographische Kapillaranalyse läßt sich die Amylose in zwei Komponenten auftrennen. Diese sind jedoch nicht mit den beiden sich im Polymerisationsgrad unterscheidenden Amylosefraktionen A1 und A2 nach K. H. MEYER identisch. Die Fraktionen A1 und A2 geben papierchromatographisch praktisch gleiche Chromatogramme, die auf zwei verschiedene Komponenten in jeder Amylosefraktion, unabhängig von deren Polymerisationsgrad, hinweisen. Während die Hauptmenge der vorliegenden Amylose mit dem Laufmittel nur etwas aufsteigt und eine stationäre Zone bildet, vermag ein anderer Anteil der Amylose, der in größerer Menge, insbesondere in aus dem Stärkeverbande in festem Zustand isolierter Amylose, anzutreffen ist, mit dem Laufmittel zu wanderm. Durch säurehydrolytischen Abbau der Amylose oder noch deutlicher bei Einwirkung von Amylase läßt sich zeigen, daß ein Angriff auf die Amylosekomponente der stationären Zone zur Komponente führt, die mit der Wasserfront zu wandern vermag. Diese wird ihrerseits zu einer mit Jod Violettfärbung gebenden, bei Verwendung von wäßrigem Alkali als Laufmittel zu einer mit der Alkalifront wandernden Komponente, einem höheren Dextrin, weiter abgebaut.
Co(II) acetylacetonate, a radical initiator
Authors: Zafar M. M. , Yousafzai A. H. K. , Mahmud Ruqia 
Published: April 2003

AbstractThe bulk polymerisation of methyl methacrylate and the studies of the resulting polymers have revealed the radical mechanism of initiation with Co(II) acetylacetonate. Copolymerisation studies of styrene/methyl methacrylate, styrene/acrylonitrile, and methyl methacrylate/acrylonitrile under similar conditions, using azoisobutyronitrile, benzoyl peroxide, Mn(III) acetylacetonate, and Co(II) acetylacetonate, have also shown the identical nature of the mechanism of initiation of these initiators. The tacticity of the polymer, deduced from NMR spectra, is identical with that of a polymer prepared with a conventional free radical initiator.