bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polythiolester. II. Polythiolactid
Authors: Bührer Von Heinrich G. , Elias Hans‐Georg 
Published: April 2003

AbstractThiomilchsäure‐S‐carbonsäureanhydrid (4‐Methyl‐1.3‐oxathiolan‐2.5‐dion, 3‐Thia‐4‐methylbernsteinsäureanhydrid, TMSCA) wurde mit verschiedenen optischen Reinheitsgraden (D93L7, D50L50, D29L71) synthetisiert. Racemisches TMSCA besitzt einen Schmelzpunkt von 46°C, optisch reines (D‐ oder L‐)TMSCA einen von 62°C. TMSCA polymerisiert im festen Zustand (Sublimation, Umfällen). Primäre und sekundäre Amine sowie Wasser sind Polymerisationsinitiatoren; die Polymerisationsgeschwindigkeit ist aber in Dioxan‐Lösung sehr gering. Tertiäre Amine initiieren nicht. Optisch aktive Amine induzieren eine stereoselektive Polymerisation. D93L7‐Polythiolactid weist nach Messungen der optischen Rotationsdispersion in Chloroform keine Helixstruktur auf. (−)‐Dithiolactid wurde zu Vergleichsmessungen durch Pyrolyse von Polythiolactid synthetisiert.
The synthesis and properties of some aromatic polythioethers
Authors: Baron Arthur L. , Blank David R. 
Published: April 2003

AbstractPolyarylene sulfides have been prepared from 4.4′‐biphenyldithiol and 4.4′‐biphenyl‐ether dithiol by reaction with 4.4′‐dichlorodiphenylsulfone. These polymers were oxidized to the corresponding polysulfoxides using hydrogen peroxide. The thermal properties of the polysulfoxides prepared were investigated and compared with those of their polythio‐ether precursors.
Reactivity of mono‐epoxides toward silk fibroin
Authors: Shiozaki Hideki , Tanaka Yoshio 
Published: April 2003

AbstractThe addition reaction of various mono‐epoxides such as epichlorohydrin, glycidol, allylglycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, propylene oxide, styrene oxide, hexadecene oxide, and vinyl cyclohexene monoepoxide with silk fibroin was investigated in the presence of some salts in different solvents at 30–80°C. Histidine, lysine, arginine, aspartic acid and glutamic acid, serine and tyrosine reacted. The weight gains decreased with increasing solubility parameter of the solvents, reached a minimum value at about 10 or at the solubility parameter of the epoxide, and then increased with the parameter. The salt effects on the epoxide‐silk reaction were described partly by the hydration ability or by the acidity of the cations, and also by the basicity or the nucleophilicity of the anions. The substituent effects of the epoxide on the add‐ons were elucidated by the modified TAFT equation, (log k − log k0)/σ* = ρp + ρsEs/σ*, where k0 and k are the rate constants for the reaction of a given compound and for the same reaction of one of its derivatives; σ* is the polar substituent constant characteristic of the substituent, Es is the steric substituent constant, and ρp and ρs are the reaction constants as measure of the susceptibility of the reaction to the polar and steric effects of substituents.
The hydrodynamic behaviour of amylose tricarbanilate in dilute solution. V. The estimation of the unperturbed dimensions of amylose tricarbanilate from measurements carried out in good solvents
Authors: Banks W. , Greenwood C. T. 
Published: April 2003

AbstractTheories which separate short‐ and long‐range forces are applied to the experimental results for amylose tricarbanilate (ATC) in a good solvent (pyridine). The unperturbed dimensions obtained in this manner from light‐scattering, viscosity, and sedimentation measurements are compared with those obtained experimentally using a pyridine/water theta‐mixture. Satisfactory agreement is found when the FLORY‐OROFINO, or KRIGBAUM, treatment of the second virial coefficient is used, and also when the FIXMAN expression is applied to the measured coil dimensions. The apparent good agreement between the measured unperturbed dimensions and those obtained by means of the COWIE‐BYWATER treatment of the frictional coefficient is shown to be fallacious. Application of the STOCKMAYER‐FIXMAN treatment to viscosity measurements also leads to erroneous coil dimensions. Deviations from the hydrodynamic theories are shown to be due to the ATC macromolecule behaving as a partially free‐draining coil.Basic criteria to be satisfied in order to determine the unperturbed coil dimensions of polymers from measurements made in a good solvent are suggested.
Solvent effects in radical copolymerization. I. Acrylamide
Authors: Saini Guido , Leoni Alvaro , Franco Simone 
Published: April 2003

AbstractAcrylamide has been free radical copolymerized with styrene and methyl methacrylate at 70°C in different solvents (dioxane, dioxane/ethanol mixture, ethanol). A strong influence of the solvent on the copolymer compositions has been observed; particularly copolymers richer in acrylamide have always been obtained in dioxane.These results indicate that the nature of the solvent (polarity, dielectric constant etc.) could affect the polarity and the reactivity of the acrylamide double bond as well as the stability of the growing radical. Other factors are also discussed.
Stereokontrolle. V. Radikalische Polymerisation von vinylformiat
Authors: Elias Hans‐Georg , Riva Marcello , Göldi Paul 
Published: April 2003

AbstractVinylformiat wurde in Substanz, Aceton, Chloroform bzw. Dimethylformamid bei Temperaturen zwischen +60 und −20°C radikalisch polymerisiert. Aus der Temperaturabhängigkeit des Verhältnisses Xi/Xs an isotaktischen und syndiotaktischen Diaden wurde die Differenz der Aktivierungsenthalpien (ΔHi≠ − ΔHs≠) bzw. ‐entropien (ΔSi≠ − ΔSs≠) für die Polymerisation in den einzelnen Lösungsmitteln berechnet. Zwischen (ΔHi≠ − ΔHs≠) und (ΔSi≠ − ΔSs≠) besteht ein Kompensationseffekt. Aus der Kompensationstemperatur T0 = 344°K der Stereokontrolle wird geschlossen, daß die Stereokontrolle mindestens teilweise durch Wasserstoffbrückenbindungen im übergangszustand bedingt ist.
Solvent effect in radical copolymerization. II. N.N‐dimethyl acrylamide
Authors: Saini Guido , Leoni Alvaro , Franco Simone 
Published: April 2003

AbstractThe free radical copolymerization of N.N‐dimethyl acrylamide with styrene or methyl methacrylate has been carried out at 70°C in solvents of different dielectricity constants. The present work does not show the strong solvent influence on copolymer compositions previously found for acrylamide copolymerizations. The influence of the presence of two alkyl groups on the amidic nitrogen is discussed. The calculated copolymerization parameters agree with the values obtained by other authors.
Bestimmung des Wechselwirkungsparameters χ und des Molekulargewichtes Mc an vernetzten Polymeren
Authors: Mula Angelo , Chinellato Luigi 
Published: April 2003

AbstractEs wird eine Methode beschrieben, die die Bestimmung des Wechselwirkungsparameters Polymer‐Quellungsmittel χ und des Mol.‐Gew. Mc zwischen zwei Netzpunkten direkt an vernetzten Polymeren erlaubt.Die Methode beruht auf Messungen der Drücke, die das vernetzte Polymere ausübt, wenn es in einem geschlossenen Volumen quillt.Die Methode wird auf Naturkautschuk, Acrylnitril/Butadien/Styrol‐Copolymeres (ABS) und Polyurethan angewandt, und die Ergebnisse werden mit Literaturangaben verglichen.
Estimation of endgroups in poly(vinyl acetate) and the corresponding poly(vinyl alcohol) to study the hydrolysis reaction
Authors: Vidyarthi Dinesh K. , Mukhopadhyay Sailes , Palit Santi R. 
Published: April 2003

AbstractThe mode of branching in poly(vinyl acetate) has been studied using reverse dye partition (RDP) technique developed in this laboratory. It has been observed that during hydrolysis of poly(vinyl acetate) the degree of polymerization of the polymer decreases in all cases. This degradation is found to be erratic. It may be caused by the separation of branches which were connected to the main chain through ester linkage. This idea has been confirmed by the detection of average one carboxyl endgroup in the resulting shorter polymer chains.The change in the number of endgroups in the parent and the corresponding hydrolysed polymer has been used as a tool for the estimation of number of branches in poly(vinyl acetate) molecules.
Zur Problematik der Endgruppenbestimmung nach Abbruch der Ziegler‐Natta‐Polymerisation mit Jod oder tritiiertem Alkohol. 10. Mitt. Zur Polymerisation mit metallorganischen Mischkatalysatoren
Authors: Schnecko H. , Jung K. A. , Grosse L. 
Published: April 2003

AbstractBeim Abbruch der Polymerketten in heterogenen Ziegler‐Natta‐Systemen mit Jod zeigt sich, daß die Bestimmung der Jodendgruppen durch mikroanalytische Titration zu den gleichen Ergebnissen führt wie die Neutronenaktivierungsanalyse. Die J‐Bestimmung in Blindproben führt zu der Erkenntnis, daß die Temperaturabhängigkeit des Abbruches mit Jod und mit Alkohol ganz verschieden ist.Für den an sich zu bevorzugenden Kettenabbruch mit tritiiertem Alkohol zeigt sich, daß die Bestimmung des scheinbaren Isotopeneffektes in jedem Fall erneut durchzuführen ist; dabei können ganz unterschiedliche Werte erreicht werden. Schließlich wird beim Abbruch mit tritiiertem Alkohol gefunden, daß die Metall‐Polymerbindungen bevorzugt reagieren und schon mit geringen Mengen an Abbruchreagenz vollständig abgebrochen werden.
Etude par diffusion de la lumière et par équilibre de sédimentation en gradient de densité de l'hétérogénéité en composition des copolymères statistiques
Authors: Lamprecht J. , Strazielle Cl. , Dayantis J. , Benoit H. 
Published: April 2003

AbstractOn a examiné le problème que pose la détermination expérimentale de la polydispersité en composition des copolymères statistiques azéotropes par les méthodes de la diffusion de la lumière et de l'équilibre de sédimentation en gradient de densité. Cette étude a été réalisée sur deux échantillons de copolymères statistiques styrène/méthacrylate de méthyle. On a montré en particulier que la méthode de la diffusion de la lumière reste valable pour déterminer les hétérogénéités en composition mais qu'elle présente certaines difficultés dans sa réalisation pratique.
Flüssige phasenpaare zur fraktionierung hochmolekularer polymethacrylsäureester
Authors: Tavel Peter V. , Bieri Vinzenz 
Published: April 2003

AbstractFlüssige Phasenpaare zur Gegenstromfraktionierung hochmolekularer Polymethacrylsäureester (Mol.‐Gew. 60 000–600 000) nach dem Molekulargewicht und nach Estergruppen sind auf möglichst rationelle Weise gesucht worden. Als geeignet haben sich fast kritische Phasenpaare von Mehrkomponenten‐Systemen erwiesen. Sie bestehen aus einem Polymerlösungsmittel und zwei verschieden polaren Komponenten, die sich gegenseitig nicht mischen, wohl aber mit dem Polymerlösungsmittel. Eine 4. Lösungsmittelkomponente ist erforderlich, um für die multiplikative Verteilung günstige Verteilungskoeffizienten einzustellen oder das Polymere in die Gegenphase überzuführen. Sie entscheidet, in welcher Phase sich das Polymere anreichert, während der Abstand des Phasenpaares vom kritischen Punkt, gemessen am Phasendichteunterschied, die Größe des Verteilungskoeffizienten und die Lösungskapazität bestimmt. Für die Verteilung von Polymethacrylsäuremethyl‐und‐ äthylestern eignet sich das fast kritische System aus n‐Hexan/Aceton/Wasser. Der Methylester geht vollständig in die polarere, der äthylester in die unpolarere Phase. Bei Zugabe kleiner Mengen Benzol bzw. Essigsäure treten die Ester vollständig in die Gegenphase über. Diese Mengen sind vom Molekulargewicht des Polymeren unabhängig. Mit Phasenpaaren richtig eingestellter Zusammensetzung läßt sich ein Gemisch des Methyl‐ und äthylesters im Scheidetrichter durch 1–2 maliges Ausschütteln quantitativ trennen. Methyl/äthyl‐Mischester zeigen Verteilungskoeffizienten, die zwischen denjenigen der reinen Ester liegen. Die Phasenpaare sollten für die Fraktionierung von Mischestern nach ihrem Gehalt an Estergruppen geeignet sein. Hierzu sind aber besondere Verteilungszentrifugen erforderlich, die in Entwicklung begriffen sind.
Studies in addition polymerization in mixed solvent system part VI. Chain transfer of aromatic amines in the polymerization of methyl methacrylate
Authors: Bhattacharyya Bhupati Ranjan , Nandi Uma Shankar 
Published: April 2003

AbstractChain transfer constants of amines have been determined in the polymerization of methyl methacrylate using the mixed‐solvent method. The transfer constants are in the order of aniline < methyl aniline < dimethyl aniline. The chain transferring ability of amines has been explained in the light of the polar structure of the transition state. Substitution enhancing electron donating capacity of the amine nitrogen results in higher transferring ability. The decrease in the rate of polymerization due to amines, is in the same order as that of chain transferring capacity and is explained on the basis of hyperconjugation. The estimation of amino end group in the polymer by dye‐partition technique supports the mechanism suggested for transfer reaction of amines.
The role of oxygen in the oxidative polymerization of 2.6‐xylenol catalyzed by copper‐amine complexes
Authors: Tsuchida Eishun , Kaneko Masao , Nishide Hiroyuki 
Published: April 2003

AbstractThe role of oxygen in the oxidative polymerization of 2.6‐xylenol by copper‐amine complexes was studied. It was found that using an excess of a copper‐pyridine (Py) complex the polymerization proceeds even in the absence of oxygen, but that with an excess of a copper‐aliphatic amine (n‐butylamine or diethylamine) complex, oxygen is indispensable for the coupling to occur. It is concluded that oxygen promotes the electron transfer from the coordinated monomer to the metal ion or the dissociation reaction of the activated monomer, probably by forming a complex with the intermediate. Due to the π electron‐accepting property of the Py ring the Py‐copper complex is active even in the absence of oxygen. On the other hand, the aliphatic amine‐copper complex is active only when oxygen, which has an electron‐accepting ability, is coordinated. According to the kinetic equation derived on the basis of complex formation between oxygen and the catalyst, the reciprocal of the reaction rate constant (k2) is proportional to the reciprocal of the partial pressure of oxygen in the system; this is in agreement with the experimental results. The effect of the solvent (Py and o‐dichlorobenzene) is discussed.
Studies on homologous series of oligomeric antioxidants derived from p‐cresol/formaldehyde condensates. III. Evaluation in an ethylene/propylene copolymer
Authors: Huglin M. B. , Kay Edna , Knight G. J. , Wright W. W. 
Published: April 2003

AbstractThe effectiveness of compounds of the type
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as antioxidants in an ethylene/propylene (EP) copolymer has been examined and the results compared with those for some commercial high molecular weight antioxidants. Increasing the mol. wt. of the additive was found to improve its antioxidative efficiency and also to reduce the degree of interference with cure. Comparison with the results of earlier work1 showed that the efficiency of the antioxidants was affected by the nature of the polymer substrate.
Réaction de substitution nucléophile sur le polyméthacrylate de méthyle. I. Réaction du méthylsulfinyl sodium à température ambiante
Authors: Arranz F. , Galin J. C. 
Published: April 2003

AbstractNous avons étudié la réaction du méthylsulfinyl sodium (dimsylsodium) sur le polyméthacrylate de méthyle en solution homogène dans le diméthylsulfoxyde. A température ambiante et pour des degrés de substitution inférieurs à 30%, les réactions secondaires de cyclisation intramoléculaires sont négligeables; la substitution nucléophile s'effectue alors de façon sélective sur les groupements ester, sans dégradation ni réticulation, pour conduire avec des rendements quantitatifs à des copolymères binaires, homogènes en composition, porteurs de groupements latéraux céto‐β‐sulfoxyde, COCH2SOCH3, dont le méthylène activé présente une acidité assez élevée.L'étude morphologique de ce copolymère en solution diluée dans le diméthylformamide montre que les dimensions non perturbées et le coefficient de rigidité de la chaǐne du copolymère demeurent voisins de ceux du polyméthacrylate de méthyle initial, mais que, par contre, les interactions polymère—solvant sont devenues bien plus intenses dans le cas du copolymère par suite des possibilités de solvatation spécifique des unités substituées céto‐β‐sulfoxyde.
Über die elementarprozesse bei der anionischen polymerisation des styrols in tetrahydropyran (THP)
Authors: Böhm L. L. , Schulz G. V. 
Published: April 2003

AbstractKinetische und konduktometrische Messungen am System Polystyrl‐Natrium in THP werden mit dem Ziel durchgeführt, alle in dem früher vorgeschlagenen dreiteiligen Reaktionsschema vorkommenden thermodynamischen und kinetischen Parameter zu bestimmen und mit den in anderen Lösungsmitteln gefundenen Werten zu vergleichen. Es zeigt sich, daß die Geschwindigkeitskonstanten der Monomeraddition an das Kontaktionenpaar, das solvatgetrennte Ionenpaar und das freie Anion, die sich um Größenordnungen unterscheiden, vom Lösungsmittel nur geringfügig beeinflußt werden. Der ungewöhnlich große Einfluß der Lösungsmittel auf die Polymerisationsgeschwindigkeit geschieht durch Verschiebung der Gleichgewichte zwischen den genannten Formen der Kohlenstoff‐Natriumbindung.
Studies on the mechanism of the ring opening polymerization of cycloolefins with particular reference to cycloolefin copolymerizations
Authors: Dall'Asta G. 
Published: April 2003

AbstractThe ring opening polymerization of cycloolefins in the presence of widely different transition metal catalysts leads to unsaturated polyalkenamers. The evolution of this reaction and of the catalysts is illustrated.Cycloolefin copolymerizations have allowed to elucidate aspects concerning the site of ring opening for different catalysts and classes of cycloolefins. Further studies and observations refer to the transition state and to the stereochemistry of the cycloolefin coordination.The comparison of the cycloolefin copolymerization and the cycloolefin insertion into preformed polyalkenamers allows deductions concerning the permanence of the catalytic centers.Some properties of regular model polymers derived from hydrogenated poly(methylalkenamer)s are compared with those of the corresponding ethylene/propylene copolymers.
Aqueous polymerization of methacrylamide initiated by KMnO4/H2C2O4 redox system
Authors: Misra G. S. , Gupta C. V. 
Published: April 2003

AbstractThe polymerization of methacrylamide initiated by potassium permanganate/oxalic acid redox system has been studied at 35 ± 0.2°C in a nitrogen atmosphere. The rate of polymerization is independent of the activator (oxalic acid) concentration within the range 5·10−3 to 10·10−3 mole·1−1, except at very high (above 10·10−3 mole·1−1) or at very low (below 5·10−3 mole·1−1) concentrations of the activator. The rate varies linearly at low monomer concentration (up to 5.87·10−2 mole·1−1). The catalyst exponent decreases from nearly unity (0.91) to 0.66 with increase in concentration of the catalyst (KMnO4) probably due to participation of primary radicals in the termination of the growing chain. The addition of strong acid (H2SO4) within the range 5 · 10−4–15 · 10−4 mole · l−1, shows a constant pH of 2.7 resulting in no change in initial rate. With activator alone (H2C2O4 · 2H2O), within the pH range 2.7 to 2.9 an optimum is observed. The initial rate increases with increase in polymerization temperature. The overall energy of activation as calculated from the ARRHENIUS plot has been found to be 15.1 kcal · mole−1 within the temperature range 30–50°C.Organic solvents (water miscible only) depress the initial rate and the maximum conversion. Small amounts of neutral salts (KCl and Na2SO4), however, show no appreciable effect on the polymerization rate, but small amounts of manganous salts (MnSO4) can increase the initial rate to a considerable extent. High concentrations of MnSO4 result in termination of the growing chain. A complexing agent, Na2F2, decreases the initial rate but increases the maximum conversion. Introduction of fresh catalyst at intermediate stages of polymerization increases both the rate of the reaction and the conversion.
Computer simulation of successively solutional fractionation of macromolecules
Authors: Kamide Kenji , Sugamiya Ken 
Published: April 2003

AbstractThe successive solution fractionation (SSF) (i.e., the successive solvent extraction of coacervate) was simulated by using an electronic computer. A polymer having the most probable distribution of number average degree of polymerization, X0n = 150, and weight average degree of polymerization, X0w = 300, was hypothetically fractionated, on the basis of the generalized FLORY‐HUGGINS‐FUJISHIRO theory in which the concentration dependence of the polymer/solvent interaction parameter, expressed as p, was taken into account. As p is increased the composition of the fraction with a larger degree of polymerization (X), obtained by SSF, decreased, while the smaller X region remained almost constant. The composition of the fraction in the region of the smaller X is much smaller than that obtained from successive precipitation fractionation (SPF). The fractionation data (Xw and the amount of the fraction) were analyzed according to the treatment of SCHULZ and of KAMIDE et al. The results revealed that the first one is preferable to the second one in the case of SSF. The broadness of the molecular weight distribution in the fraction markedly decreased with decrease in the initial concentration of polymer, v0p, if v0p was higher than 0.1%. An asymtotic, limiting value for Xw/Xn of an extremely small fraction of polymer, separated by SSF, was appreciably larger than that from SPF, but the corresponding value for the standard deviation was zero. The molecular weight distribution of the fractions becomes narrower as their amount is smaller. This behaviour is in contrast to the case of SPF. In SSF, a decreasing in the relative amount of each fraction, besides that of an initial concentration, effectively enables fractions of narrow distribution to be obtained.
The radical initiation of vinyl polymerization by α.α.α′.α′‐Tetrasubstituted dibenzyls
Authors: De Jongh H. A. P. , De Jonge C. R. H. I. , Huysmans W. G. B. , Sinnige H. J. M. , De Klein W. J. , Mijs W. J. , Jaspers H. 
Published: April 2003

AbstractThe radical polymerization of styrene, methyl methacrylate and acrylonitrile is initiated by α.α′‐dicyanodibenzyls α.α′‐disubstituted with ester, nitrile, amide or phenyl groups in the temperature range 60 to 100°C and by α.α.α′.α′‐tetracarboxymethyldibenzyl at 100 to 110°C. Vinylacetate and vinylchloride show a low reactivity.The overall polymerization rate constants Kp have been determined dilatometrically for styrene initiated by a large number of dibenzyls and comparable peroxides. The styrene polymerization curves are generally comparable with those of peroxides. A notable exception is tetracyanodibenzyl.The strong influence of α‐ and ring‐substituents in the dibenzyls on the styrene polymerization rate is discussed. The stereochemistry is also important : the meso α.α′‐dicyanodibenzyls α.α′‐disubstituted with ester groups give a 2.5 to 3.5 fold faster polymerization than their dl isomers.The initiator efficiency is related to the kd values, determined from NMR line width measurements. The α.α′‐ dicyanodibenzyls α.α′‐disubstituted with ester groups are good initiators, while those with phenyl groups and nitrile groups are inefficient.Relevant to initiation and termination, the 1.2‐addition of some of the dimers to styrene at 120 to 150°C has been studied with chemically induced dynamic nuclear polarization (CIDNP).