bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydride ion transfer processes and cationic polymerization of cyclic acetals
Authors: Penczek Stanisław 
Published: April 2003

AbstractFour topics related to the cationic polymerization of cyclic acetals and mainly based on the author's results are reviewed.
The kinetics of the H− transfer from linear and cyclic acetals and ethers to the triphenylmethyl cation were examined. A linear correlation between the 1H‐NMR shift of the H‐atom to be transferred as H− anion and the enthalpy of activation (ΔH) was observed for H− donors which are linear and cyclic‐planar or deviate slightly from planarity. Puckered rings, like 1,3,5‐trioxane were found to be very poor H− donors. A linear relationship between ΔH and ΔS was observed for all studied compounds.
The equilibria carbenium ion ↔ oxonium ion involving the unpaired triphenylmethyl cation and different linear and cyclic acetals and ethers were studied. A linear relationship between the basicity of the involved nucleophile (expressed as pKa or pKb) and the enthalpy of equilibrium (ΔH) was found.
The chemistry of the elementary reactions leading eventually to the formation of the active species in the polymerization of 1,3‐dioxolane was investigated. The latter was used as a model monomer and initiated with triphenylmethyl salts with various stable anions like AsF and SbF or with the unstable SbCl. The importance of the ambident reactivity of 1,3‐dioxolan‐2‐ylium cations was pointed out and the kinetics of cationation via ring opening of these salts was described.1,3‐Dioxolan‐2‐ylium salts were shown to be sufficiently stable to be slowly transformed into the linear cations (k̄cat ≈ 10−3 to 10−4 mol−1 dm3 s−1 at 25°C). This slow reaction was partially responsible for the induction periods observed in the polymerization of 1,3‐dioxolane.
The kinetics and mechanism of the chain propagation of 1,3‐dioxolane were described and a structure (20) was proposed for the growing centres. It was indicated that the growing species, being the tertiary oxonium ions use the polymer segments as ligands and in contrast to the oxycarbenium ions do not abstract hydride anions (H−).
Zur ermittlung der struktur und unverträglichkeit von pfropfcopolymeren durch messungen der lichtstreuung und phasentrennung in lösung
Authors: Kuhn Rainer , Alberts Heinrich , Bartl Herbert 
Published: April 2003

AbstractTheoretische Betrachtungen zeigen, daß man bei Pfropfcopolymeren durch Lichtstreuungsmessungen in Lösung außer den Molekulargewichten und Trägheitsradien der Pfropfäste auch die Unverträglichkeit der Pfropfäste mit der Pfropfunterlage ermitteln kann, wenn das verwendete Lösungsmittel isorefraktiv mit der Pfropfunterlage ist, und man den Gewichtsanteil an Pfropfästen kennt.Die neue Methode der Unverträglichkeitsbestimmung aus anomalen Zimm‐Diagrammen wird an Mischungen aus Polystyrol und einem chemisch einheitlichen statistischen Äthylen/Vinylacetat‐Copolymeren geschildert und auf Fraktionen von entsprechenden Pfropfcopolymeren angewandt.Die Ergebnisse der Lichtstreuung werden mit den Ergebnissen der Phasentrennung aus Trübungspunktmessungen verglichen.
Study of the isothermal bulk polymerization of vinyl acetate by differential scanning calorimetry
Authors: Može Adolf , Vizovišek Ivan , Malavašič Tatjana , Černec Franc , Lapanje Savo 
Published: April 2003

AbstractThe course and kinetics of the isothermal bulk polymerization of vinyl acetate were studied by differential scanning calorimetry. The initiator used was 2,2′‐azoisobutyronitrile. The polymerization was investigated at temperatures between 55 and 70°C at constant initiator concentration, 5,0.10−2 mol/l. The heat of polymerization at 60°C is – 19,5 kcal/mol and decreases with increasing temperature. Initial rate constants for the polymerization were also determined and from them the overall activation energy, 21,6 kcal/mol. Another series of polymerization experiments were performed at 60°C with variable amounts of the initiator. The overall rate of polymerization at low degrees of conversion depends on the square root of the initiator concentration which is in agreement with the assumed kinetic scheme.
Kernresonanzspektroskopische mikrostrukturanalyse von vinylchlorid‐propen‐copolymeren, 1. NMR‐spektroskopische bestimmung der bruttozusammensetzung und der kompositiven triaden für vinylchlorid‐propen‐copolymere
Authors: Sielaff Günter , Hummel Dieter O. 
Published: April 2003

AbstractCopolymere aus Vinylchlorid (VC) und Propen (P) wurden durch hochauflösende magnetische Protonenresonanz bei 100 MHz untersucht. Aus dem Vergleich mit den Homopolymerspektren konnten die Resonanzkomplexe der Copolymerspektren zugeordnet, die Bruttozusammensetzung der Copolymeren ermittelt und die Copolymerisationsparameter berechnet werden.Der Methinresonanzkomplex der VC‐Einheiten ließ sich durch Spinentkopplung in fünf Peaks aufspalten. Ihre Zuordnung zu kompositiven und konfigurativen Triaden erfolgte anhand eines graphischen Trennverfahrens. Das zur Ermittlung der Copolymerisationsparameter verwendete Wachstumsmodell wurde mit den gemessenen Triadenhäufigkeiten auf seine Gültigkeit hin geprüft.
Kernresonanzspektroskopische mikrostrukturanalyse von vinylchlorid‐propen‐copolymeren, 2 NMR‐spektroskopische bestimmung der taxieparameter aus den häufigkeiten konfigurativer triaden
Authors: Sielaff Günter , Hummel Dieter O. 
Published: April 2003

AbstractCopolymere aus Vinylchlorid (VC) und Propen (P) wurden durch hochauflösende magnetische Protonenresonanz bei 100 MHz untersucht. Die Methylresonanz der P‐Einheiten und die entkoppelte Methinresonanz der VC‐Einheiten konnten anhand eines graphischen Trennverfahrens konfigurativen Triaden zugeordnet werden.Es wurde eine graphische Darstellung entwickelt, die sowohl die Werte der Cotaxieparameter Σs und Σp liefert als auch ein Test für das “ultimate model” ist. Aus der Abhängigkeit der Cotaxieparameter von der Polymerisationstemperatur konnten die Aktivierungsenthalpien der taktischen Wachstumsschritte ermittelt werden.
Versuche zum thermischen abbau von copolyamiden aliphatischer und aromatischer aminocarbonsäuren
Authors: Kricheldorf Hans R. , Leppert Elmar 
Published: April 2003

AbstractAn Gemischen niedermolekularer Carbonsäureamide sowie an Gemischen von Polyamiden mit Carbonsäureamiden oder anderen Polyamiden wurde nachgewiesen, daß Umamidierungsreaktionen bei 200°C nur in geringem Umfang und sehr langsam eintreten, bei 250°C jedoch rasch ablaufen. Der thermische Abbau von Copolyamiden aliphatischer und aromatischer Aminocarbonsäuren erfolgt fast ausschließlich durch Spaltung von Bindungen der aliphatischen Aminocarbonsäure. Dabei werden 4‐Aminobutyryl‐ und 5‐+ninovaleryl‐Reste bevorzugt als Lactame abgespalten, während bei α‐, β‐ und ε‐Aminoacylresten verschiedene Abbaureaktionen nebeneinander ablaufen. Die Lactamabspaltung kann ab ca. 250°C auch aus der Kette heraus erfolgen, führt dann aber nicht zum Kettenbruch, da die ursprünglich benachbarten Aminocarbonsäurereste bei der Lactamabspaltung wieder miteinander verknüpft werden. Das thermische Verhalten der Copolyamide wird mit den Eigenschaften niedermolekularer Modellsubstanzen verglichen und die Reaktionsmechanismen diskutiert.
Copolymerisation von aminosäure‐alkenylestern
Authors: Geckeler Kurt , Bayer Ernst 
Published: April 2003

AbstractRadikalische Copolymerisationen einer Reihe von Aminosäure‐alkenylestern (1a–e) mit 1‐Vinyl‐2‐pyrrolidinon (2) und 2,2′‐Azoisobutyronitril als Starter werden beschrieben. Die erhaltenen Polymere sind sowohl in Wasser als auch in zahlreichen organischen +ösungsmitteln leicht löslich und können als Trägerpolymere zur Synthese von Peptiden verwendet werden. Aus dem Copolymer 3a, aus 2 und N‐tert‐Butyloxycarbonylalanin‐vinylester (1a), wird nach Abspaltung der Aminoschutzgruppe 3b erhalten, an das eine weitere Aminosäure gekuppelt wird. Dies zeigt, daß an den dargestellten Copolymeren polymeranaloge Umsetzungen durchgeführt werden können.
Préparation, polymérisation et réticulation du méthacrylate de (diméthyl‐2,2 dioxolann‐1,3 yle‐4) méthyle. Hydrolyse des polymères obtenus
Authors: Beinert Gérard , Hild Gérard , Rempp Paul 
Published: April 2003

AbstractLa préparation du méthacrylate de (diméthyl‐2,2 dioxolann‐1,3 yle‐4) méthyle (4) a été mise au point par réaction en milieu HMPT/éther d'un mélange d'acide méthacrylique et de chlorure de thionyle avec l'O‐isopropylidène‐2,3 glycérol (3).La polymérisation anionique de ce monomère donne naissance à des polymères de faible polydispersité en masse moléculaire.Si le poly[méthacrylate de (diméthyl‐2,2 dioxolann‐1,3 yle‐4) méthyle] [poly(4)] α,ω‐d+arbanionique «vivant» est utilisé comme promoteur pour la polymérisation d'une +ible quantité de diméthacrylate d'éthylène, la réaction conduit à la formation de réticu+ +odèle homogènes caractérisés par la longueur quasi‐constante de leurs éléments linéaires.L'hydrolyse acide de la fonction acétal du poly(4) linéaire conduit au poly(méthacrylate de dihydroxy‐2,3 propyle).
Living radical polymerization of styrene and its block copolymerization with methyl methacrylate
Authors: Horie Kazuyuki , Mikulášová Darina 
Published: April 2003

AbstractThe existence of living polymer radicals in emulsion polymerization with a macromolecular heterogeneous initiator has been ascertained by preparing block copolymers of styrene with methyl methacrylate. Polymerization of styrene initiated by oxidized polypropylene and triethylenetetramine (3,6‐diaza‐1,8‐octanediamine) proceeds even after the removal of the initiator from the emulsion, reaches 100% conversion, and methyl methacrylate newly added to the system undergoes further polymerization. The molecular weight of polystyrene and of the block copolymer increases with the conversion. The yield of pure block copolymer is about 90% under optimal conditions. The turbidimetric titration curve of the block copolymer shows a characteristic plateau region and suggests monodispersity of the copolymer. Reasons for the absence of termination in this system are presented. This type of living radical polymerization offers some advantages for the preparation of block copolymers, as compared with the anionic living polymerization.
Polymères α,α'‐diméthylxylyléniques, 3. Copolycondensation du bis(chloro‐1 éthyl)‐1,4 benzène avec des hydrocarbures aromatiques mononucléaires
Authors: Iovu Mircea , Tudorache Elena 
Published: April 2003

AbstractNous avons étudié des réactions de copolycondensation du bis(chloro‐1 éthyl)‐1,4 benzène (1) avec le benzène, le toluène, le m‐ et le p‐xylène, le mésitylène et le tétraméthyl‐1,2,4,5 benzène.Les réactions de copolycondensation étudiées donnent des produits à structure tridimensionnelle (infusibles et seulement partiellement solubles) měme dans le cas de tétraméthyl‐1,2,4,5 benzène où c'était à prévoir d'obtenir un produit linéaire.
Über die bestimmung der strömungsdispersion zur ermittlung von molekulargewichtsverteilungen mit der gelchromatographie
Authors: Berger Knud C. 
Published: April 2003

AbstractDie Kenntnis der axialen Dispersion ist eine notwendige Voraussetzung zur Ermittlung von Molekulargewichtsverteilungen aus der gelchromatographischen Elutionskurve. Die vorliegende Arbeit beschäftigt sich mit der Bestimmung der axialen Dispersion unter Verwendung monodisperser Polymerer. Abschließend wird ein Verfahren vorgeschlagen, welches aus der gelchromatographischen Elutionskurve von Proben mit bekannter Molekulargewichtsverteilung die Dispersion näherungsweise zu ermitteln gestattet.
Structural and thermodynamic characteristics of chlorinated polyethylenes, 1
Authors: Erä Väinö A. 
Published: April 2003

AbstractA series of suspension chlorinated and chlorosulfonated polyethylenes (CPE and CSPE resp.) of varying chlorine contents were investigated. The composition of the CPE polymers was determined from DSC measurements and specific volume determinations. Structural differences between CPE and CSPE polymers were confirmed by IR spectra and the heats and entropies of fusion.
Polymerization of β‐propiolactone by metal acetylacetonates and carboxylates
Authors: Kaeriyama Kyoji 
Published: April 2003

AbstractSome metal acetylacetonates and carboxylates are effective for the polymerization of β‐propiolactone (2). The activity depends on the metallic ion. Heterochelates containing 2,2′‐dipyridyl or 1,10‐phenanthroline and acetylacetone as ligands have a large effect due to the tertiary amine groups. Titanocene dichloride is an effective promoter for these polymerizations. The combination of titanocene dichloride and metal acetylacetonates has an activity for the polymerization of 2‐chloroethyl vinyl ether, which neither component has separately.
Zum mechanismus der anionischen copolymerisation polarer ungesättigter monomere
Authors: Artamonowa Irina , Klenin Stanislaw , Troitskaya Alla , Erussalimsky Boris 
Published: April 2003

AbstractFür Copolymere, die sich bei kleinen Umsätzen in den Systemen Acrylnitril (AN)‐Methylacrylat (MA) – Toluol – Butyllithium (BuLi) und AN‐MA‐Toluol‐Dipropylbutyllithiumcarbinolat (DPBL) bilden, wurde eine Uneinheitlichkeit der chemischen Zusammensetzung festgestellt. Der relative Anteil verschiedener Fraktionen und deren Zusammensetzung werden durch die Reaktionstemperatur und den Typ des Initiators beeinflußt. Diese Erscheinung wird der Koexistenz von aktiven Zentren mit verschiedenen Gegenionen zugeschrieben. Eine derartige Koexistenz kann entweder durch die Bildung von Nebenprodukten aus einer Reaktion zwischen Initiator und den Monomeren (System mit BuLi), oder durch die Dissoziation der assoziierten Lithiumderivate (System mit DPBL) verursacht sein.
Polymerisation of trioxane, 2. Kinetics of the reaction initiated by chlorosulphonic acid
Authors: Raman P. S. , Mahadevan V. 
Published: April 2003

AbstractThe kinetics of polymerisation of trioxane, initiated by chlorosulphonic acid have been studied in o‐dichlorobenzene, trichloroethylene, and carbon tetrachloride. The reaction is shown to be simple, though the kinetics are different in the above solvents. With very pure and dry substrates, no induction period is observed. Rate parameters have been evaluated.
Studies on metal chelating polymers, 3. Metal chelates of cationic polymers containing the 3‐formyl‐ or the 3‐acetyl‐4‐hydroxybenzyl group in the side chain
Authors: Haruta Masami , Harada Susumu 
Published: April 2003

AbstractThe stability constants for several metal complexes (Cu(II), Ni(II), Zn(II), Co(II), Fe(III), Al(III)) of terpolymers from diallyl[3‐formyl (or 3‐acetyl‐) 4‐hydroxybenzyl]methylammonium chloride, diallyldimethylammonium chloride, and sulfur dioxide were determined by potentiometric titration.The results are discussed comparing the stability constants with those of o‐hydroxybenzaldehyde and o‐hydroxyacetophenone derivatives.
Organometallic compound with lewis base, 3. Polymerization mechanism of vinyl compounds by aluminum alkyl‐lewis base complex
Authors: Ikeda Masanori , Hirano Tsuneo , Nakayama Shinichi , Tsuruta Teiji 
Published: April 2003

AbstractComplexes of aluminum alkyl (AlR3), formed with certain kinds of Lewis bases, induce anionic polymerization of polar vinyl compounds such as acrylonitrile (AN) or methyl methacrylate (MMA), whereas AlR3 by itself cannot polymerize AN and MMA anionically. When the ligand Lewis base is bidentate, the resultant complex with a formal coordination number of five shows high catalytic activity for anionic polymerization even if the basicity of the ligand is small. On the other hand, when the ligand Lewis base is monodentate, the complex is four‐coordinated and shows catalytic activity for the polymerization of AN and MMA only when the basicity of the ligand is sufficiently large. The initiation reaction for the polymerization of 1‐substituted vinyl compounds such as MMA should be the conjugate addition of one alkyl group of the activated AlR3 to the monomer. With 1‐unsubstituted vinyl compounds such as AN or methyl acrylate (MA), a part of the initiation and the chain transfer reactions seem to take place through the abstraction of the 1‐hydrogen of the vinyl monomer molecules.
Oxidative polymerization of 2,6‐dimethylphenol with semiconducting organic polymeric metal complexes containing the bis(ethylene‐1,2‐dithiolato)copper (II) structure, 1
Authors: Kaneko Masao , Manecke Georg 
Published: April 2003

AbstractIn the oxidative polymerization of 2,6‐dimethylphenol (8) the catalytic activities of the following semiconducting organic polymeric metal complexes were studied: polymeric complexes containing bis(ethylene‐1,2‐dithiolato)Cu(II) or Fe(III) complexes and copper(II) phthalocyanine structures (3a–c), catalysts consisting of bis(ethylene‐1,2‐dithiolato)‐Cu(II) or Fe(III) complex structures and hemiporphyrazine type structures (5a–c), and also polymers containing a copper complex of dimercaptomaleic acid monoamide (7). It was found that a suspension of the insoluble bis(ethylene‐1,2‐dithiolato)Cu(II) polymeric complexes of type 3 catalyzes the polymerization in the presence of oxygen in pyridine at room temperature producing poly[oxy‐(2,6‐dimethyl‐1,4‐phenylene)] (9) in very good yields. Polymeric complexes of type 5 were inactive by themselves. However, we showed that bis(ethylene‐1,2‐dithiolato)Cu(II) polymeric complexes of both the 3 and 5 type possess great activities if they are used in the presence of small amounts of copper(II)‐pyridine complex in pyridine solution (the chosen concentration was so low that the Cu(II)‐pyridine complex alone had only a small activity). Bis(ethylene‐1,2‐dithiolato)Fe(III) complexes of both the 3 and 5 type were inactive even in the presence of the Cu(II)‐pyridine complex.
Oxidative polymerization of 2,6‐dimethylphenol with semiconducting organic polymeric metal complexes containing the bis(ethylene‐1,2‐dithiolato)‐copper(II) structure, 2
Authors: Kaneko Masao , Manecke Georg 
Published: April 2003

AbstractIf an insoluble polymeric complex 1 which possesses both the bis(ethylene‐1,2‐dithiolato)Cu(II) a Cu(II)phthalocyanine type structure is treated with a pyridine solution of the Cu(II)‐pyridine complex in a low concentration, the filtrate obtains a high activity for the oxidative polymerization of 2,6‐dimethylphenol. This might be due to a partial decomposition followed by a partial dissolution of the polymer complex. The catalytic behaviour of the soluble part of the polymeric complex 1 was studied. The activity of this mixed catalyst system consisting of Cu(II)Py and the soluble part of 1 was found to be 6–50times higher than that of Cu(II)Py alone under the applied conditions.
Photosensitized polymerization of butyl acrylate under high pressure
Authors: Yokawa Masaru , Ogo Yoshiaki , Imoto Tatsuya 
Published: April 2003

AbstractThe propagation and termination rate constants for butyl acrylate polymerization under high pressure at 30°C were measured by the rotating sector method.The effect of pressure on the individual rate constant was determined and the activation volumes for the propagation and the termination were obtained as −22,5 cm3/mol and 20,8 cm3/mol, respectively, and the overall activation volume was −26,3 cm3/mol. The rate constant and its dependence on pressure were compared with data previously obtained on methyl methacrylate and butyl methacrylate polymerizations, and the problem concerning the differences of the pressure effect between these reactions were discussed.
Non‐Newtonian behavior of cellulose solutions
Authors: Riandes Evaristo , Pereña José M. 
Published: April 2003

AbstractThe gradient dependence of viscosity was studied for fractionated cellulose in cadoxene and in cadoxene/water (1:1). The present experiments were performed in the shear stress range 1,4 to 1 000 dyn/cm2 (1,4.10−5 to 10−2 newton/cm2). The experimental results, viewed in the light of various theories, show that the excluded volume effects and the internal viscosity play an important role in non‐Newtonian behavior of cellulose solutions.
Chain conformation in linear polyethylene and paraffins defined by four NMR‐components
Authors: Phaovibul Orapin , Loboda‐Čačković Jasna , Čačković Hinko , Hosemann Rolf 
Published: April 2003

AbstractA systematic investigation of a series of nuclear magnetic resonance spectra (NMR) of differently treated polyethylene (PE) and paraffin samples, indicates that all observed spectra can be analysed unequivocally as the sum of four standard functions which are attributed to four components, α, β1, β2, and γ, of increasing proton mobility. In some spectra most of the components are clearly separated from each other. The shape of their derivatives is therefore directly measurable and symmetric for the α‐component. For β1 the derivative is that of a Gaussian and for γ that of a Lorentzian function. β2 alone is not directly observable but appears as a remainder in the spectra of melt‐crystallized PE. It exhibits the shape of the derivative of a Lorentzian function, too. The basic hypothesis is that each of these four components maintains his characteristic shape even if they overlap each other. The line widths ΔH are: 13,2 to 17,9 Gauß (1 Gauß = 10−4Vs m−2), 3,0 to 6,0 Gauß, 0,85 to 1,2 Gauß, and 0,04 to 0,18 Gauß, depending on the history of the sample. The α‐component is assigned to protons in the microparacrystalline phase (regular backfolding included), fixed chain ends and tight tie‐molecules. In hotstretched PE the latter enlarge the α‐component by 4% without changing the “crystallinity” measured by the density. γ is assigned to longer chain ends undergoing micro‐Brownian motion. The more regular the lamella surface, the smaller is the contribution to the β1 and β2 component.So‐called single crystals of PE e.g. have only 0,02% γ, which increases during melt‐crystallization to ca. 0,1% (sample MPE 5). Its extremely high value of 0,4% in all drawn samples (DPE) is attributed to an enlarged number of longer mobile endsegments generated by chain scission. β1 is attributed to less mobile chain ends, chains in lateral grain boundaries, defects within the paracrystals, chainfolds and tie‐molecules in the “amorphous” parts which are of great importance for the mechanical properties. If the component β1 e.g. is smaller than 15%, melt‐crystallized PE (MPE) is always brittle. When the melt is stirred, β1 in the MPE reaches values up to 19%. The tensile strength then is larger. In extended chain crystals (ECC) β1 is reduced to about 10% of the MPE‐value. This may indicate that about 10% of the ECC still have the folded structure. This is underlined by the fact that MPE alone has a remarkable β2‐component from segments more mobile than β1 which is reduced also to about 10% in ECC. The β2‐component is attributed to loose loops and loose connecting molecules, which connect neighbouring paracrystals.
Kinetics of the aqueous polymerization of acrylamide initiated by the permanganate‐ tartaric acid redox system
Authors: Misra Gauri S. , Rebello Joseph J. 
Published: April 2003

AbstractThe kinetics of the aqueous polymerization of acrylamide, initiated by the permanganate/tartaric acid redox system was studied at 35±0,2°C under nitrogen. The initial rate of polymerization remains independent of the tartaric acid concentration in the range 3,3.10—3 to 9,9.10—3mol/dm3. The order of the reaction with respect to the catalyst concentration (catalyst exponent) is found to be 0,55, indicating a bimolecular mechanism for the termination reaction. The rate of polymerization varies linearly at low monomer concentrations (1,25.10—2 to 5,0.10—2mol/dm3). With increase in temperature above 35°C, the initial rate increases but the conversion decreases. The overall energy of activation is found to be 18,68 kcal/mol (78,10kJ/mol) in the temperature range 30 to 50°C.Water miscible organic solvents and neutral salts depress both the rate and the conversion. Addition of MnSO4 or the injection of more catalyst at intermediate stages raises both the initial rate and the maximum conversion. NaF decreases the rate but increases the conversion.