bluuebunny/crossref_metadata_2025 huggingface dataset:
On the mechanism of polymerization of methyl substituted 7‐oxabicyclo‐[2.2.1]‐heptanes
Authors: Kops Jørgen , Spanggaard Hans
Published: April 2003

The polymerization of endo‐ and exo‐2‐methyl‐7‐oxabicyclo‐[2.2.1]‐heptane with phosphorus pentafluoride catalyst in methylene dichloride and nitrobenzene has been found to proceed with increasing yield and molecular weight with decreasing temperature in the range +25°C to −30°C, but at −78°C there was no polymerization. The ring‐opening appears to proceed exclusively through nucleophilic attack at C‐1 in the alkyloxonium ion, leading to only one type of structural unit in each type of polymer. The polymers of the exo‐2‐methyl isomer are completely soluble in THF, whilst those of the endo‐2‐methyl isomer are insoluble. The solubility appears to be connected with flexibility of the chain molecule associated with the possibility for interconversion between different chair conformations for the cyclohexane ring‐structures.

By ring‐closure of 2.6‐dimethylcyclohexane‐(1.4)‐diol two isomers have been prepared and identified. The endo,exo‐2.6‐dimethyl‐7‐oxabicyclo‐[2.2.1]‐heptane gives insoluble, highly crystalline polymers with phosphorus pentafluoride catalyst in methylene dichloride. The failure of the corresponding exo,exo‐2.6‐dimethyl isomer to polymerize under identical conditions is explained by conformational analysis.
A study of the nature of the active centres in anionic polymerization
Authors: Polyakov D. K. , Baranova N. I. , Gantmakher A. R. , Medvedev S. S.
Published: April 2003

The electron absorption spectra and the electrical conductivity of two systems: 1.1‐diphenylalkyllithium/tetrahydrofuran and the dilithium compound of 9.10‐dialkyl‐9.10‐dihydroanthracene/tetrahydrofuran were studied. The investigations were carried out over a wide range of concentrations of the organolithium compounds, covering both the region of predominant ion pairs and that of high relative free ion content, according to conductometric data. It is shown for both systems studied that the electron absorption spectrum remains practically unchanged when passing from ion pair to free ions.
Kinetic studies on the reaction of formaldehyde with diphenyl sulfide. Formaldehyde resins. 99
Authors: Kunieda Norio , Suzuki Akira , Kinoshita Masayoshi , Imoto Minoru
Published: April 2003

Kinetic studies on the acid‐catalyzed reaction of formaldehyde with diphenyl sulfide (DPS) were carried out in acetic acid in the presence of sulfuric acid. The rate of the initial stage of the reaction was found to be in agreement with the following equation.

The relative rates of diphenyl sulfide and its homologous compounds in the reaction with formaldehyde gave a good correlation with BROWN‐OKAMOTO's σ⊕ values and a large ρ value. The polar effects of substituents of the substituted diphenyl sulfides on the rates were found to be considerably large. From these results a plausible mechanism of the reaction has been deduced.
Studies on homologous series of oligomeric antioxidants derived from p‐cresol/formaldehyde condensates. II. Evaluation in polystyrene
Authors: Huglin M. B. , Knight G. J. , Wright W. W.
Published: April 2003

The effectiveness of compounds of the type
magnified image
as antioxidants in polystyrene has been examined and the results compared with those for some commercial high mol. wt. antioxidants. Effectiveness was found to depend not only on mol. wt., but also on molecular structure, concentration, and temperature of use.
Syntheses and reactions of functional polymers. LXIV. Reactions of phenyl polystyryliodonium salts
Authors: Yamada Yorinobu , Okawara Makoto
Published: April 2003

Phenyl polystyryliodonium salts, containing bisulfate, thiocyanate, bromide, or trifluoroacetate as counter anion, were allowed to decompose in dimethylformamide and dioxane at 100°C. The bisulfate and thiocyanate anion preferentially, and trifluoroacetate anion selectively attacks the unsubstituted phenyl ring to give polystyrene derivatives with two components and polyiodostyrene, respectively. On the contrary, the bromide anion preferentially attacks the phenyl ring of the polystyrene side. This result was explained on the basis of the co‐operative charge transfer bonding between the aromatic ring of the iodonium salt and its adjacent aromatic ring through bromide anion. These nucleophilic substitution reactions on the polymer are investigated and compared with their model reactions.
Redox polymerisation. Kinetics of the reaction initiated by the malonic acid/Mn3⊕ system
Authors: Devi N. Ganga , Mahadevan V.
Published: April 2003

Kinetics of vinyl polymerisation initiated by the redox system malonic acid/Mn3⊕ have been investigated in the temperature range of 5‐15°C in sulphuric acid and perchloric acid media for acrylonitrile and methyl methacrylate. A mechanism involving the formation of a complex between Mn3⊕ and malonic acid whose decomposition yields the initiating free radical with the polymerisation being terminated by mutual interaction of growing radicals has been suggested.
Thermal copolymerizations of vinyl sulfides with some weak acceptor monomers
Authors: Inoue Hiroshi , Otsu Takayuki
Published: April 2003

Thermal copolymerizations of vinyl sulfides (VS) with some weak electron‐accepting monomers were studied on the basis of donor‐acceptor interaction. VS were thermally polymerized in the presence of diethyl fumarate, dimethyl maleate, acrylonitrile (AN) methyl methacrylate (MMA), methyl acrylate, and ethyl acrylate (EA) in the absence of radical initiators to yield copolymers. The monomer/copolymer composition curves for these copolymerizations were quite similar to those produced from polymerizations initiated by α.α′‐azobisisobutyronitrile, indicating that the propagating species are free radicals. Similar conclusions were obtained from experiments with the inhibitor benzoquinone, and from the small observed solvent effect, but no proof for the occurrence of cationic or anionic polymerization was obtained.

Although the existence of a 1 : 1 donor/acceptor complex in AN/VS system was spectroscopically confirmed, such interaction was appreciably weak, in comparison to that of maleic anhydride/VS. In the systems MMA/VS and EA/VS no interaction was observed. Accordingly, the intiating radical species in AN/VS system might be considered to be formed through donor/acceptor interaction. It was also found that alternative copolymers were obtained from thermal copolymerization of AN with VS in the presence of zinc chloride. The initiation mechanism for these thermal copolymerization is discussed.
Electroinitiated cationic polymerization of ethyl and i‐butyl vinyl ethers
Authors: Mengoli Giuliano , Vidotto Graziano
Published: April 2003

The electroinitiated cationic polymerization of ethyl and i‐butyl vinyl ethers has been studied under various experimental conditions using NaB(C6H5)4 as background electrolyte.

Differring from other electrolytes with higher oxidation potentials, the NaB(C6H5)4 allows appreciable current intensities and the polymerizations can occur at moderate rates.

The monomer to polymer conversion presents a slightly sigmoidal shape as a function of the quantity of electricity and at a fixed quantity of electricity is independent from the current intensities.

The molecular weights of the polymers are substantially controlled by chain transfer to monomers and solvents: the relative chain transfer constants are reported.

The reaction temperature affects remarkably the molecular weights while the influence of dielectric constant of the reaction medium is negligible.

An interpretation is given of the effect of NaB(C6H5)4 electrolyte on the initiation mechanism and on the resulting conditions of polymerization.
Studies in polymerisation of vinyl acetate. II.
Authors: Potnis S. P. , Deshpande A. M.
Published: April 2003

The effect of increase in temperature on various constants such as overall rate constant (K), the quotient of the rate constant of propagation and the square root of the constant of termination (Kp/Kt1/2), rate constant for initiation (KI), transfer constants due to the monomer and initiator (CM), (CI), respectively, and chain transfer constant due to solvent (CS) has been studied in detail by the polymerisation of vinyl acetate in bulk as well as in glacial acetic acid at 65°C with benzoyl peroxide and at 50 and 60°C with azobisisobutyronitrile as initiators. A comparative study of the results obtained has been made.
Polyreaktionen in orientierten systemen. II.. Polymerisation von 4‐vinylpyridinium‐salzen in micellar geordneten lösungen
Authors: Mielke I. , Ringsdorf H.
Published: April 2003

Die Kinetik der „spontanen”︁ Polymerisation von 4‐Vinylpyridiniumperchlorat in Wasser zeigt, daß oberhalb einer „kritischen”︁ Konzentration ein Wechsel des Polymerisationsmechanismus eintritt entsprechend einer Änderung in der Struktur des sich bildenden Polymeren. Untersuchungen der Viskosität und der Oberflächenspannung an Modellsubstanzen zeigen, daß dieses Phänomen der Bildung von Micellen und der darin ablaufenden Polymerisation zuzuschreiben ist. Der alkalische Abbau der Polymeren wurde untersucht.
Polyhydrochinonsulfone. VI. Darstellung eines redoxharzes auf der basis von (2‐vinylsulfonyl)‐naphthohydrochinon‐(1.4)
Authors: Manecke Georg , Rühl Christian‐Steffen , Wehr Gregor
Published: April 2003

(1.4‐Diacetoxy)‐(2‐vinyl‐sulfonyl)‐naphthalin wurde dargestellt. Durch Copolymerisation des Monomeren mit Styrol und p‐Divinylbenzol und anschließende Sulfonierung und Verseifung des Polymeren wurde ein Redoxharz erhalten, dessen Austausch‐ und Redoxkapazität bestimmt wurde.
Anionic polymerization of cyclic sulfides initiated by metal complexes of aromatic nitriles and ketones
Authors: Panayotov Ivan M. , Berlinova Iliyana V.
Published: April 2003

The capacity of metal complexes of aromatic nitriles and ketones to initiate the polymerization of ethylene sulfide, propylene sulfide and styrene sulfide is studied by means of spectral and chemical methods. The results indicate that the polymerization of styrene sulfide initiated by anion‐radicals of the used nitriles and ketones proceeds via electron transfer from the initiator to the monomer, while ethylene sulfide polymerizes by way of valence bond formation between the initiator and the monomer. The polymerization of propylene sulfide is a multistage reaction linked with the formation of propylene and initiator species. The polymerization of all three monomers initiated by aromatic nitrile dianions proceeds by electron transfer.
Pre‐exponential factors of rate constants of chain propagation reactions in free radical polymerization
Authors: Guaita Marino
Published: April 2003

A method is described for calculating the pre‐exponential factor of the chain propagation rate constants in free radical vinyl polymerizations taking place in the liquid phase. The pre‐exponential factors calculated for some typical monomers are in satisfactory agreement with the experimental values.
Vergleich der zahl aktiver zentren und einiger kinetischer konstanten bei der polymerisation von äthylen, propylen und buten‐1 mit ZIEGLER‐NATTA‐katalysatoren. 11. Mitt. Zur polymerisation mit metallorganischen mischkatalysatoren
Authors: Jung K. A. , Schnecko H.
Published: April 2003

Für die drei Olefine, Äthylen, Propylen und Buten‐1, werden mit dem Katalysatorsystem TiCl3/Al(C2H5)2Cl in Abhängigkeit von der Polymerisationszeit gemessen: der Polymerisationsverlauf, die Zahl der Metall‐Polymer‐Bindungen (über Endgruppenbestimmung nach Abbruch mit tritiiertem Alkohol) und die Viskosität der gebildeten Polymeren. Aus diesen Daten lassen sich die Polymerisationsgeschwindigkeit, die Konzentration an aktiven Zentren, die Uneinheitlichkeit sowie weitere Reaktionskonstanten bestimmen. Die Ergebnisse werden diskutiert; sie lassen den Schluß zu, daß sich ein im Ausgangszustand gleiches Katalysatorsystem monomerspezifisch verhält und verändert.
The effect of ionizing radiation on the thermal properties of an ethylene/propylene copolymer
Authors: Melia T. P. , Salpadoru N. , Wilkinson J.
Published: April 2003

The results of heat of fusion measurements on an ethylene/propylene copolymer (containing 27 mole‐% propylene), which had been subjected to different doses of gamma radiation (0–620 Mrad) at 298°K are described. The dependence of both the enthalpy and entropy of fusion on radiation dose is similar to that observed previously with isotactic polypropylene.
The addition halogenation of polyalkenamers. I. Synthesis and properties of the homologous series of poly(1.2‐dihaloalkamer)s
Authors: Dall'Asta G. , Meneghini P. , Gennaro U.
Published: April 2003

The addition chlorination and bromination of a series of polyalkenamesr

where n varies from 2 to 10, yield a homologous series of poly(1.2‐dihaloalkamer)s

Substitution halogenation is completely avoided by operating in methylene chloride solution. Experimental features of the halogenations are examined. No appreciable degradation of the polymers accompanies the halogenation reaction. Some physical properties of poly‐(1.2‐dihaloalkamer)s are reported and compared with those of chlorinated polyethylenes. Many of the polymers exhibit X‐ray crystallinity by well oriented fibre spectra and first order transition at DTA analysis.
Relation between pH and viscosity of some poly(alkylvinylpyridine N‐oxides) in aqueous solution
Authors: Holt Paul , Tamami Bahman
Published: April 2003

The variation with pH of the viscosities of aqueous solutions of the following polyvinylpyridine oxide derivatives has been studied, viz. atactic poly(2‐vinylpyridine 1‐oxide), poly(2‐methyl‐6‐vinylpyridine 1‐oxide), poly(3‐methyl‐2‐vinylpyridine 1‐oxide), poly(5‐ethyl‐2‐vinylpyridine 1‐oxide), poly(4‐vinylpyridine 1‐oxide), poly(3‐methyl‐4‐vinylpyridine 1‐oxide) and poly(2‐methyl‐5‐vinylpyridine 1‐oxide), and mainly isotactic poly(5‐ethyl‐2‐vinylpyridine 1‐oxide).

When the vinyl group is in the 3 or 4 position, viscosity is maximal between pH 6 and 10, probably because polymer chains are cross‐linked by water molecules attached to N‐oxide groups. Poly(methyl‐2‐vinylpyridine 1‐oxides) give a pH/viscosity curve that is roughly the inverse of this with a minimal viscosity within this pH range. These polymers probably take up a tightly packed conformation near neutrality due to bonding between N‐oxide and α‐H of the polyvinyl chain. More than one conformation is possible and an attempt has been made to interpret the positions of the viscosity peaks in terms of the possible conformations.
Zur verzögernden wirkung aromatischer aldehyde auf die radikalische polymerisation von vinylverbindungen
Authors: Kämmerer Hermann , Mück Karl‐Friedrich , Janz Birgit
Published: April 2003

Die Einwirkung einer Reihe aromatischer Aldehyde auf die mit α.α‐′Azobisisobuttersäurenitril gestarteten Polymerisationen von Styrol und Methacrylsäuremethylester wurde untersucht (a) durch Vergleich der Polymerausbeuten; (b) durch quantitative Analyse der UV‐Spektren der gereinigten Polymeren und (c) durch Vergleich ihrer M̄n‐ und M̄n‐Werte. Bei der Styrolpolymerisation zeigen 4‐Phenyl‐benzaldehyd und Indol‐3‐aldehyd keine Einwirkung. 4‐Phenylazo‐benzaldehyd, Benzaldehyd, Anthracen‐9‐aldehyd und m‐(2.4‐Dinitrophenoxy)‐benzaldehyd verzögern die Polymerisation. Bis auf Benzaldehyd wird hierbei ihr kovalenter Einbau in das Polystyrol nachgewiesen. Für 4‐Phenylazo‐benzaldehyd konnte eine scheinbare Übertragungskonstante bestimmt werden. Bei der Polymerisation von Methacrylsäuremethylester wird entweder inhibierende, verzögernde oder keine Einwirkung der Aldehyde beobachtet; sie werden sämtlich nicht eingebaut. Jedoch zeigen die Molekulargewichte der Polymethacrylsäuremethylester eine Erniedrigung, die bisher nicht erklärt werden kann.
Application de la chromatographie sur gel à l'étude des polyéthylènes ramifiés
Authors: Prechner Roland , Panaris René , Benoit Henri
Published: April 2003

L'utilisation conjointe de la chromatographie sur gel et des mesures viscosimétriques permet de définir un indice moyen de ramification. La comparaison de cet indice avec celui obtenu en associant la chromatographie sur gel et les mesures directes de masse moléculaire permet d'apprécier l'hétérogénéité en degrés de ramification d'un échantillon donné. La méthode est appliquée à quelques échantillons commerciaux de polyéthylène haute pression.
Study of radical polymerization by means of ESR. I. Homogeneous polymerization of styrene
Authors: Bresler S. E. , Kazbekov E. N. , Fomichev V. N. , Shadrin V. N.
Published: April 2003

An extremely sensitive instrument for ESR measurements in liquid media was developed on the basis of a new principle of registration of the ESR signals. By means of this device the spectrum of macroradicals of polymerizing styrene was recorded, and the stationary concentration of growing chains was measured quantitatively. Thus the first direct data for the chain propagation constant of the radical polymerization of styrene were obtained.
Morphology of epitaxially crystallized poly‐γ‐benzyl‐L‐glutamate
Authors: Rybnikar F. , Geil P. H.
Published: April 2003

Epitaxial crystallization of poly‐γ‐benzyl‐L‐glutamate (PBLG) on 001 alkali halide single crystal surfaces results in block and row structures that are qualitatively similar for various solvents and crystals used. There is a definite tendency in the first stages of epitaxial crystallization to align the α‐helical molecules along the 〈110〉 substrate direction. We propose that the epitaxial structures are built up of straight, non‐folded α‐helical molecules associated side‐by‐side and, in the case of low M̄w fractions, also end‐to‐end. The epitaxial crystallization of PBLG was observed only in the vicinity of the precipitation point. The orienting and attracting forces coming from the crystal substrate have a long range character and are of at least two kinds. The decoration effect of PBLG epitaxial structures could be used for substrate surface structure characterization.
Untersuchungen über die γ‐struktur in unverstrecktem und verstrecktem 6‐polyamid
Authors: Illers K. H. , Haberkorn H. , Simák P.
Published: April 2003

Die in der monoklinen α‐Struktur kristallisierten Bereiche des unverstreckten und verstreckten 6‐Polyamids wandeln sich bei der Behandlung mit wäßriger Jod‐Alkalijodid‐Lösung in die γ‐Struktur um. Diese γ‐Struktur wird röntgenographisch, IR‐spektroskopisch und kalorimetrisch eingehend untersucht.

Verglichen mit der bei schneller Abkühlung aus der Schmelze oder bei der Kaltkristallisation entstehenden γ*‐Struktur hat die γ‐Struktur eine gute Ordnung, die sich durch Tempern noch erheblich verbessern läßt. Die gut geordnete γ‐Struktur besitzt keine hexagonale, sondern eine monokline oder orthorhombische Elementarzelle und eine Kristalldichte von 1,190 g/cm3. Sie ist im Gegensatz zur γ*‐Struktur thermisch sehr stabil und geht beim Erwärmen unmittelbar in die Schmelze über. Proben mit γ‐ und solche mit γ*‐Struktur zeigen denselben Zusammenhang zwischen Schmelzwärme und spezifischem Volumen und besitzen einen übereinstimmenden Wert für die Dichte der amorphen Bereiche (1,090g/cm3), der mit dem der Dichte einer völlig amorphen Probe übereinstimmt. Die Schmelzwärme des γ‐Kristalls beträgt 51 cal/g. Die in den Röntgendiagrammen und IR‐Spektren vorhandenen Unterschiede zwischen Proben mit γ‐ und γ*‐Struktur werden diskutiert.
Copolymères séquencés poly(oxyéthylène)/poly(oxyéthylène‐oxyadipoyl) à charnières uréthane
Authors: Galin Monique , Galin Jean Claude
Published: April 2003

Nous avons étudié la cinétique de la réaction du bis(4‐isocyanatophényl)méthane (MDI) et du l‐méthyl‐2.4‐diisocyanatobenzène (2.4‐TDI) sur le poly(oxyéthylène) (POE, M̄n = 2750) et le poly(oxyéthylèneoxyadipoyl) (PAE, M̄n = 2350) en solution dans le toluène ou le dioxanne, et pour un rapport constant [NCO]/[OH] = 2. Il est possible d'obtenir, dans des conditions expérimentales bien déterminées, des «prépolymères» porteurs de groupements terminaux isocyanate. Ces «prépolymères» présentent cependant une stabilité limitée dans le temps, qui se manifeste par un accroissement de la masse moléculaire moyenne et de la fonctionnalité, résultant de la formation de liaisons allophanate intermoléculaires. Ce processus est en particulier accéléré dans le cas des POE.

La polycondensation en solution homogène entre «prépolymère» PAE ω.ω′‐diisocyanate et POE conduit à des copolymères séquencés linéaires, dans lesquels le nombre moyen de séquences (3 à 20) et la longueur de la séquence POE (2750 ≤ M̄n ≤ 10600) peuvent varier dans un assez large domaine. L'architecture de ces macromolécules est caractérisée par l'alternance régulière de séquences hydrophobes PAE et hydrophiles POE reliées entre elles par des charnières uréthane. Ces matériaux constituent des modèles intéressants dans le domaine des copolymères séquencés cristallisables doués de propriétés amphipatiques, et dans celui des élastomères polyuréthane.
Über die struktur der polyketone aus äthylen und kohlenmonoxid
Authors: Hoyer Herbert , Fitzky Hans‐Georg
Published: April 2003

Die 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

The 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

A 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

The 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

By 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

The 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

The 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

Radical 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

Zur 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

In 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

The 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

The 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

The 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

The 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

The 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

Electrochemically 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

The 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

L'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

Les 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

Au 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

L'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

Investigations 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

Die 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

The 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.
Modification des polyméres de vinyl‐4 benzophénones méthoxylées et copolymérisation des monomères avec le styréne
Authors: Pinazzi Chr. P. , Fernandez A.
Published: April 2003

Les monomères cités ont été copolymérisés radicalairement dans le benzene avec le styrène. La composition des copolymères a été déterminée à partir de leurs spectres NMR. Les constantes r1 et r2 été détérminée d calculdes; dans ce cas, les p‐vinylbenzopédnones méthoxy‐lées ont une plus grande réactivité que le styrene. Les homo et copolymkres de ces p‐vinyl‐benzophdnones n'ont aucun effet protecteur contre le rayonnement UV. La condition nécessaire pour obtenir cet effet est la pédsence d'un groupement hydroxyle en position ortho par rapport au groupement carbonyle. La déméthylation partielle des polyméres des vinyl‐4 méthoxy‐2′ benzophénones a été étudiée dans ce but. Cette réaction a permis d'obtenir en particulier la poly(viny1‐4 hydroxy‐2′ mdthoxy‐4′ benzophenone) dont le spectre UV indique un effet protecteur contre la lurnière naturelle.
Self polycondensation of oxalyl dihydrazide
Authors: Lehtinen Arja , Sundquist Jorma
Published: April 2003

In order to obtain a linear poly(1,3,4‐oxadiazole‐2,5‐diyl) the self‐polycondensation of oxalyl dihydrazide has been investigated. Polymers with molecular weight up to 6000 were prepared by solution polycondensation in N‐methylpyrrolidone containing lithiumchloride. These polymers are thermally stable up to 300°C. They were characterized by IR spectra, thermal analysis and solubilities.
Aqueous polymerization of methacrylamide initiated by acidified bromate/thiourea redox system
Authors: Misra G. S. , Gupta C. V.
Published: April 2003

The polymerization of methacrylamide initiated by acidified bromate/thiourea has been studied at 35 ± 0,2°C in a nitrogen atmosphere. The rǒle of the acid (HCl) is to convert thiourea to isothiourea with a faster rate in contrast to a neutral or alkaline medium, and thus producing free radicals by oxidation of the latter. The rate of polymerization is independent of the activator (thiourea) concentration within the range of 0,4–1,0 · 10−2 mol/dm3 or very low (0,4 · 10−2 mol/dm3) concentrations of the activator. The rate varies linearly at low monomer concentration (up to 17,64 · 10−2 mol/dm3). The catalyst exponent comes out to be unit (1,1) in the studied range of the catalyst (KBrO3) concentration. This might be due to the collision of an active centre with a chain breaking agent. The addition of a strong acid (HCl) within the pH range of 1,75–1,9 results in no change of the initial rate; the maximum conversion decreases, however, with the activator alone, an optimum being observed at pH 1,9. The initial rate and the limiting conversion increase with the increase in polymerization temperature up to 35 ± 0,2°C. The overall activation energy has been found to be 18,9 Kcal/mol within the temperature range of 25–45°C.

Organic solvents (only water miscible) and small amounts of neutral salts (KCl and Na2SO4) depress the initial rate and the maximum conversion. The addition of Na2F2 does not show any variation in the polymerization rate in contrast to Cu‐ and Fe‐Salts.