bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the pressure and concentration dependence of the sedimentation coefficient
Authors: Cantow Manfred J. R. , Porter Roger S. , Johnson Julian F. 
Published: April 2003

AbstractIn the ultracentrifugation of solutions in organic solvents the sedimentation coefficient has to be corrected for two effects: the increasing dilution of the solution due to the sector shape of the centrifuge cell and the increasing density and viscosity of the solvent caused by the effective field of gravity. The corrections can amount to 10–30% of the measured value. A new graphical method of correcting for both effects without the need for any additional data is described. This technique in combination with established procedure also allows calculation of an average molecular weight of the solute.
Die Ultrazentrifuge als Kriterium für molekulare Einheitlichkeit. Grenze des Auflösungsvermögens und der Empfindlichkeit
Authors: Bodmann Von O. , Kranz D. , Mutzbauer H. 
Published: April 2003

AbstractDie Gradientenkurve einer zusammengesetzten, in der Ultrazentrifuge sedimentierenden Grenzschicht von zwei Komponenten wird auf Grund einfacher Voraussetzungen berechnet, welche praktisch z. B. bei einer Mischung der α‐Amylasen aus Bacillus subtilis und Humanspeichel zutreffen. Dabei wird ein Ausdruck für das Auflösevermögen der Sedimentation in Einheiten molekularer und apparativ vorgegebener Konstanten abgeleitet:

Diskontinuität der Verteilung der Sedimentationskoeffizienten vorausgesetzt, ist danach für die Ausbildung getrennter Maxima in der Gradientenkurve ein Mindestunterschied der Sedimentationskoeffizienten erforderlich, welcher sich nach dieser Formel mit dem Wert A > 1 abschätzen läßt.Die rechnerische Behandlung des Modells zeigt ferner, daß bei Mengengleichheit der beiden Komponenten von A > 0,5 an bereits durch eine Analyse der Kurvenform sichtbar gemacht werden kann, daß die Modellsubstanz nicht einheitlich ist. Die Anwendung dieser Methode setzt allerdings konzentrationsunabhängige Sedimentation und Diffusion voraus.Das empfindlichste Kriterium für eine einheitliche Sedimentation beruht auf dem Vergleich des scheinbaren Diffusionskoeffizienten, der aus der sedimentierenden Grenzschicht ermittelt wird, mit dem wirklichen Diffusionskoeffizienten, der auf unabhängigem Wege zusätzlich bestimmt werden muß.Dieses Kriterium kann auch dort herangezogen werden, wo lineare Konzentrationsabhängigkeit des Sedimentationskoeffizienten vorliegt, wenn der störende Einfluß der Selbstschärfung der Grenzschicht nach FUJITA berücksichtigt wird. Bei gewöhnlicher experimenteller Genauigkeit beginnt die Empfindlichkeit des letzten Verfahrens gegenüber uneinheitlicher Sedimentation, wenn der Abstand der beiden Sedimentationskoeffizienten einen Wert überschreitet, der durch A > 0,25 abgegrenzt werden kann.
Ions, ion‐pairs, and their agglomerates
Authors: Szwarc M. 
Published: April 2003

AbstractThe concepts of ion‐pairs, solvent separated ion‐pairs, and of higher agglomerates is reviewed. The conditions under wich these concepts are justified are outlined. Relations between conductance and the ion association is examined. The effect of solvents upon the association, the mobility of ions, their degree of solvation, etc. are discussed.
Poly‐(pearfluoralkylen)‐benzimidazole
Authors: Burmeister Von D. , Sander M. , Bergert K. H. 
Published: April 2003

AbstractBei der Herstellung von Poly‐(perfluoralkylen)‐benzimidazolen tritt neben HF vor allem CO2 als Zersetzungsprodukt auf. Die gebildeten, fluorhaltigen Benzimidazole sind oberhalb 250°C unbeständig, wie an Hand von reinen Modellsubstanzen gezeigt wurde. Der Abbaumechanismus ist so verwickelt, daß er nicht auf einfache Weise geklärt werden kann.
Polychelatsiloxane 2. Mitt.: Polykondensation von siliciumfunktionellen metallchelaten
Authors: Hofer Von A. , Kuckertz H. , Sander M. 
Published: April 2003

AbstractDurch Addition von (CH3)2SiHCl und CH3SiHCl2 an die Beryllium‐ und Aluminium‐chelate des 4,4‐Diacetylbuten‐1 (Allylacetylaceton) ließen sich die entsprechenden siliciumfunktionellen Silylpropylchelate in hoher Reinheit und Ausbeute herstellen. Hydrolyse und Polykondensation führten im Falle des bifunktionellen Be‐Chelates zu linearen Polychelat‐siloxanen, die bei etwa 70°C erweichen, aber erst oberhalb 200°C schmelzen. Hydrolytische Polykondensation von tri‐, tetra‐ und hexafunktionellen Chlorsilylchelaten ergab vernetzte, pulverige Polymere; gleichzeitig trat in gewissem Umfang hydrolytische Spaltung der Metallbindung ein.
A model of the chain conformation of an isotactic vinyl polymer, having optically active side groups
Authors: Allegra G. , Corradini P. , Ganis P. 
Published: April 2003

AbstractIn this paper a mathematical treatment is developed for the developed for the calculation of the average percentage of right‐handed and left‐handed conformations of isotactic polymer chains having asymmetric side groups, all with the same optical sign, in unperturbed solution. This method derives the partition function of the infinite chains by a matrix formulation, allowing for neighbor interactions according to the ISING model; it leads to results which are in qualitative agreement with the experimental values of the optical rotation exhibited by polymer solutions at various temperatures.
Crystal structure of hexagonal polythiomethylene
Authors: Carazzolo Gianalvise , Valle Giovanni 
Published: April 2003

AbstractThe crystal structure of hexagonal polythiomethylene is described. It has a hexagonal unit cell with a = 5.07 Å. and c = 36.52 Å. The polymer chains are helicoidal with the axis of the helix parallel to c. In the unit cell are comprised 17 CH2Sunits and 9 turns of the helix.
Synthesis of optically active polymers by asymmetric catalysts. IV. Dialkylzinc – alcohol system as catalyst for asymmetric‐selective polymerization of propylene oxide
Authors: Inoue Shohei , Yokota Yoshihisa , Yoshida Norimasa , Tsuruta Teiji 
Published: April 2003

AbstractThe system diethylzinc/optically active alcohol was examined as catalyst for asymmetric‐selective polymerization of propylene oxide. Optically active alcohols with rigid structure are effective for the asymmetric selection. D(–)‐1‐Methoxypropanol‐2 as well as poly(D‐propylene oxide) of low molecular weight with hydroxyl end groups select L(–)‐propylene oxide. „Catalyst control”︁ mechanism of the stereoselection in the polymerization is suggested on this and other bases.
A critical consideration of the molecular weight distribution of narrow‐distribution polymers
Authors: Ueda Minoru 
Published: April 2003

AbstractNumerical fractional solution was applied to a narrow‐distribution polymer having SCHULZ‐ZIMM type distribution (xn = 2000, xw/xn = 1.05) by using a solubility equation based on FLORY‐HUGGINS' theory. Fractions obtained by a series of ten trials overlap extensively with each other and have xw/xn values comparable to the initially given one. Application of the usual SCHULZ method to the data obtained gave a distribution far narrower than the initially given one especially in the lower molecular weight region. On the other hand, a reasonable distribution was obtained when the fractionation data were analyzed in terms of the new method proposed by HOMMA et al. This seems to justify the proposal of HOMMA et al. and their results obtained by sedimentation velocity method.
Synthetische lineare polymere XV.: Die abhängigkeit einiger spezifischer eigenschaften polymerhomologer oligomerverbindungen von der molekülgröße
Authors: Géczy Von I. 
Published: April 2003

AbstractZwischen dem Molekulargewicht einzelner Glieder von polymerhomologen Reihen und solchen spezifischen Eigenschaften, welche von additiven Größen abgeleitet werden können, ist folgender Zusammenhang gültig: \documentclass{article}\pagestyle{empty}\begin{document}$\Phi _{{\rm sp}} = \frac{a} {m} + b$\end{document}, wobei Φsp irgendeine spezifische Eigenschaft, \documentclass{article}\pagestyle{empty}\begin{document}${z}.{B}.\frac{{\gamma ^{1/4} }}{d}$\end{document} = spezifisches Parachor, \documentclass{article}\pagestyle{empty}\begin{document}$- \frac{{\gamma ^{1/4} }} {d}{\rm log (}n{ - 1)}$\end{document} = spezifisches Refrachor, \documentclass{article}\pagestyle{empty}\begin{document}$\frac{x} {d}$\end{document} = spezifische magnetische Suszeptibilität, \documentclass{article}\pagestyle{empty}\begin{document}$\frac{{2,9\ {\rm log}\ {\rm log }\eta { }}} {{\rm d}}$\end{document} = spezifische Viskositätszahl, \documentclass{article}\pagestyle{empty}\begin{document}$\frac{{v^{1/3} }} {d}$\end{document} = spezifische Schallgeschwindigkeit, n = Brechungsindex, \documentclass{article}\pagestyle{empty}\begin{document}$\frac{{n^2 + 1}} {{n^2 + 2}} \cdot \frac{1} {d}$\end{document} = spezifische Refraktion und M das Molekulargewicht ist. a und b sind Konstanten, deren Wert experimentell oder mit Hilfe der entsprechenden Inkremente ermittelt werden können. Der Wert der Konstante b kann zur Errechnung der Inkrementwerte der Atome des Grundmols verwendet werden. Einige dieser spezifischen Größen sind ferner zu Molekulargewichtsbestimmungen von Molekeln in der Größenordnung von 103−105 geeignet, z. B. von polymeren Weichmachern und synthetischen Fasern, hauptsächlich von Polyamiden und Polyestern.
Die anwendung der eisenrhodanidmethode zur quantitativen bestimmung des peroxidgehaltes in strahlenoxydiertem polyvinylchlorid
Authors: Zeppenfeld Von G. 
Published: April 2003

AbstractDie von YOUNG, VOGT und NIEUWLAND erstmals beschriebene Eisenrhodanidmethode wurde für die Bestimmung von aktivem Sauerstoff in Polyvinylchlorid (PVC) modifiziert.Das Prinzip der Methode besteht in der Reduktion des Peroxids in Gegenwart von Schwefelsäure durch Eisen(II)‐ionen und dem kolorimetrischen Nachweis des gebildeten Eisen(III) als Rhodanidkomplex. Die Methode gestattet den quantitativen Nachweis von Peroxiden auch in Anwesenheit ungesättigter Verbindungen. Mit einer unteren Nachweisgrenze von 1·10−6 Mol/l ist sie etwa so empfindlich wie die bekannte Methylenblaumethode. Ihr Vorteil gegenüber der letztgenannten besteht in der Verwendung stabiler käuflicher Analysensubstanzen.Zur Bestimmung des aktiven Sauerstoffs in PVC wird eine etwa 1‐proz. Lösung des Materials in Tetrahydrofuran mit einer Mischung, bestehend aus Benzol und einer Lösung der anorganischen Salze in Methanol, versetzt. Mit Hilfe dieser Methode wurde in strahlenoxydiertem PVC Hydroperoxid nachgewiesen.
Condensation polymerization of N‐dithiocarbonyl alkoxycarbonyl‐amino acids. Part I. Synthesis and condensation polymerization of N‐dithiocarbonyl ethoxycarbonyl‐amino acids
Authors: Higashimura T. , Kato H. , Suzuoki K. , Okamura S. 
Published: April 2003

AbstractN‐dithiocarbonyl ethoxycarbonyl‐amino acids (III),
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were synthesized in crystalline form from various amino acids by the addition of ethyl chlorocarbonate to dithiocarbamic acid salt obtained from amino acid and CS2 at low temperature. When the reaction was performed above room temperature, polypeptides could directly be obtained without getting III.Compounds such as III were synthesized from glycine, DL‐α‐alanine, DL‐valine, DL‐methionine, L‐leucine, glycylglycine, β‐alanine, γ‐amino‐n‐butyric acid and ε‐amino‐n‐caproic acid in this paper. III were polymerized to polypeptides in high yields in the presence of a basic catalyst or by heating; acid inhibited the polymerization of III.
Condensation polymerization of N‐dithiocarbonyl alkoxycarbonyl‐amino acids. Part. II. Condensation polymerization of N‐dithiocarbonyl ethoxycarbonyl‐DL‐α‐alanine in organic solvents
Authors: Higashimura T. , Suzuoki K. , Kato H. , Okamura S. 
Published: April 2003

AbstractThe effect of polymerization conditions on the rate of polymerization and molecular weights of resulting polymer was studied with N‐dithiocarbonyl ethoxycarbonyl‐DL‐α‐alanine.
magnified image
in toluenc, dioxane, nitrobenzene and methyl isobutyl ketone.In dioxane, which is a very suitable solvent to obtain high molecular weight polymers, the molecular weight of resulting polymer decreased with increasing monomer concentration. Basic substances accelerated the rate of polymerization, but decreased the molecular weight of resulting polymer. Water accelerated the rate of polymerization and the decrease of molecular weight was not so large.
Polybenzyl polymers I. The effect of monomer structure on polymer properties
Authors: Overhults W. C. , Ketley A. D. 
Published: April 2003

AbstractA systematic study has been made of the effect of methyl substitution in the aromatic ring on the FRIEDEL‐CRAFTS polycondensation of p‐dichloromethylbenzene and its derivatives with benzene derivatives. When the total number of methyl groups on the monomer and comonomer is four or greater, highly crystalline, low molecular weight products are formed. When the number of methyl substituents is less than four, rapid polymerization occurs to give amorphous, cross‐linked materials. By careful control of reaction conditions, however, the latter reactions can be stopped before cross‐linking takes place and relatively high‐molecular weight, non‐cross‐linked polymers can be isolated.
Polymerization of 2‐vinyl‐1,3‐dioxolane
Authors: Tada Koichi , Saegusa Takeo , Furukawa Junji 
Published: April 2003

AbstractWhen 2‐vinyl‐1,3‐dioxolane was treated at low temperature (−78 or −130°C.) with cationic catalysts, oily or semi‐solid polymer was produced. The result of alkaline hydrolysis showed that the polymeric product contained ester units whose amount was about 2 to 15 mole‐% of the total units. The remaining part of the polymer consisted of units containing the dioxolane ring. In the alkaline alcoholysis of the polymer with ethanol ethyl δ‐hydroxyvalerate was formed. These findings indicate that in the low temperature cationic polymerization of 2‐vinyl‐1,3‐dioxolane the ester unit, O(CH2)4CO, is formed in addition to the unit of vinyl polymerization. A mechanism for the formation of the ester unit has been proposed, in which the process of hydride‐shift is followed by ring‐opening of the resulting carbonium ion species of dioxolane.
Self‐polymerization of aromatic dinitrile N‐oxide
Authors: Imai Yoshio , Akiyama Masayasu , Uno Keikichi , Iwakura Yoshio 
Published: April 2003

AbstractSelf‐polymerization based on 1,3‐dipolar cycloaddition of isophthalonitrile N‐oxide and terephthalonitrile N‐oxide was attempted to prepare polyfuroxans. The polymers with inherent viscosity up to 0.15 were obtained in approximately quantitative yield. Polyfuroxans were only soluble in concentrated sulfuric acid, and indicated some degree of crystallinity.
The cationic polymerization of epoxides determination of polymer structures by NMR spectroscopy
Authors: Haubenstock H. , Naegele W. 
Published: April 2003

AbstractAlthough it is well established that the low temperature cationic polymerization of 3‐methylbutene‐1 and its homologs involves extensive rearrangement by hydride shifts, it has been shown by NMR spectroscopic analysis that the analogously constitute 1,3‐methyl‐1,2‐epoxybutane does not undergo a hydride shift when polymerized with boron trifluoride. Other epoxides of the type are shown also not to rearrange on cationic polymerization. The different behavior between the two systems is ascribed to differences in the types of carbonium ion intermediates involved in polymerization.
Organic sulfur compounds. XIX. Addition of dithiols to diallyl maleate: A new concept of polyester synthesis1
Authors: Oswald Alexis A. , Naegele Walter 
Published: April 2003

AbstractSelective free radical polyadditions of dithiols to the allylic double bonds of diallyl maleate result in polyesters having maleic unsaturation. Using aliphatic 1,2‐ and 1,3‐dithiols a stepwise preparation of such polyesters is possible since the first thiol group reacts more readily than the second. NMR spectroscopy was found to be a most useful tool in determining the course and extent of such selective reactions. The polyesters can be readily crosslinked by an ionic MICHAEL‐type addition of dithiols to their maleic double bonds. Free radical copolymerization with styrene can also be used to produce crosslinked networks.
Siloxanmodifizierte polypyromellitimide
Authors: Kuckertz Von H. 
Published: April 2003

AbstractDurch Polykondensation von 1,3‐Bis(aminopropyl)‐1,1,3,3‐tetramethyldisiloxan mit Pyromellitsäuredianhydrid bzw. Pyromellitsäurediäthylester wurden in organischen Lösungsmitteln lösliche und bei 180°C durch Spritzguß verarbeitbare Polymere erhalten. Bei Verwendung von 1,3‐Bis(m‐aminophenyl)‐1,1,3,3‐tetramethyldisiloxane als Aminkomponente entstanden spröde, wenig Iösliche, niedermolekulare Producte.
Polymerization of propylene oxide by diethylzinc/ketone catalysts
Authors: Sakata R. , Takeuchi K. , Yoshii H. , Haga K. , Onishi A. 
Published: April 2003

AbstractPropylene oxide was polymerized by diethylzine/ketone system. Cacatalytic effects of twenty‐four ketones were examined. Methyl ketones and cyclic ketones were effective as a cocatalyst for the polymerization, while alkyl ketones with longer chain and β‐diketon were not. The reaction of the catalyst formation was discussed. Crystallinity of the polymers obtained was compared with that of polymers by diethylzinc/water or diethylzine/alcohol catalyst.
Über die autoxydation CH‐aktiver polymerisationsinitiatoren. XIV. Mitt. Polymerisationen und polymerisationsinitiatoren1
Authors: Bredereck Von Hellmut , Föhlisch Baldur , Franz Raimund , Tagoe Daved , Diebel Klaus , Krämer Botho 
Published: April 2003

AbstractCH‐aktive Polymerisationsinitiatoren der allgemeinen Formel A‐CH(R)‐B (A und B: elektronenanziehende Gruppen, R: H oder Alkylgruppe) unterliegen in Gegenwart von Cu++ und Cl– der Autoxydation. Man beobachtet eine Parallele zwischen ihrer Autoxydationsgeschwindigkeit und Initiatorwirkung bei der Polymerisation von Methacrylsäuremethylester. Die Polymerisationsauslösung durch CH‐aktive Verbindungen wird daher auf ihre primäre Autoxydation zurückgeführt.
Kinetics of free‐radical polymerisation at high viscosities
Authors: Bogunjoko Julius S. T. , Brooks Brian W. 
Published: April 2003

AbstractMethyl methacrylate und styrene were polymerised by a free‐radical process in solutions which contained dissolved polymer. The molecular weights of the dissolved polymer and the concentration of the radical generator 2,2'‐azoisobutyronitrile were varied. Rate data were compatible with a reaction scheme in which the mobility of some growing radicals was influenced by the solution viscosity. Correlations between radical mobility and viscosity were more consistent with the experimental results than correlations between radical mobility and volume fraction of dissolved polymer. The possibility of primary radical termination is examined and a means of clarifying the chain termination process is suggested.
Functional monomers and polymers, 109. Asymmetric inclusion polymerization of (E)‐ and (Z)‐2‐methyl‐1,3‐pentadiene in apocholic acid canals
Authors: Mijata Mikiji , Kitahara Yasuhiro , Takemoto Kiichi 
Published: April 2003

AbstractAsymmetric inclusion polymerization of the prochiral monomers (E)‐ and (Z)‐2‐methyl‐1,3‐pentadiene (3a and 3b), in apocholic acid (2) canals was performed under various conditions to find out the factors controlling the asymmetric induction during the polymerization. Ozonolysis of the resulting polymers and subsequent transformation of the resulting 2‐methyl‐4‐oxovaleric acid (4) into its 2,4‐dinitrophenylhydrazone revealed the predominant formation of the (R)‐absolute configuration. The optical yield was high in the initial stage of the polymerization and decreased gradually as the polymerization proceeds. To obtain a high optical yield the polymerization was performed at low temperature applying a 1:1 mole ratio monomer/apocholic acid, and an irradiation dose < 1 Mrad. The optical yield amounted to 36% at maximum, which is the highest value obtained so far in the asymmetric polymerization of 1,3‐pentadiene derivatives using canal complexes or other known methods.
Synthèses de polysiloxanes organofonctionnels, 4. Les poly[(hydroxyméthyl)méthylsiloxane]s homogénes et hétérogènes
Authors: Reyx Danièle , Guillaume Pierre 
Published: April 2003

AbstractTransformations of oxy(halomethyl)methylsilanediyle units or oxy(acetoxymethyl)methyl‐silanediyle units into oxy(hydroxymethyl)methylsilanediyle units in homogeneous and heterogeneous polysiloxanes were investigated. Si‐C‐cleavage and SiOSi‐rearrangement were studied on disiloxanes and oligosiloxanes used as models of the corresponding polymers. Methanolysis of poly[(acetoxymethyl)methylsiloxane]s and their copolymers catalysed by p‐toluenesulfonic acid was applied to obtain poly[(hydroxymethyl)methylsiloxane]s and their copolymers.
Nature of polymer matrix of immobilized enzyme composites obtained by radiation polymerization of bifunctional monomers and its effect on the enzymatic activity
Authors: Kumakura Minoru , Kaetsu Isao 
Published: April 2003

AbstractCellulase was immobilized on a porous polymer matrix which was formed by radiation polymerization of bifunctional monomers such as poly(ethylene glycol) diacrylates (1), and the nature of the porous polymer matrix and its effect on the enzymatic activity was studied. The porous structure of the polymer matrix was found to change markedly with the monomer concentration and irradiation temperature. The formation of the porous structure shows a discontinuous change in the temperature region of −10 to −40°C, due to the change in polymerization phase and mechanism. The enzymatic activity is strongly related to the pore size, the degree of hydration of the polymer matrix, and the particle size of the composite. The degree of hydration of the polymer matrix varies with the number of oxyethylene units in the monomers 1.
Polymerization of methyl methacrylate initiated by a Rh(I) complex and benzoyl peroxide
Authors: Kameda Noriyuki , Ishii Emiko 
Published: April 2003

AbstractThe polymerization of some vinyl monomers initiated by carbonylchlorobis(triphenylphos‐phine)rhodium(I) (RhCl(CO)(P(C6H5)3)2) and benzoyl peroxide (BPO) was studied. The polymerization ability was found to decrease in the following order: methyl methacrylate (MMA) > styrene > vinyl acetate > isobutyl vinyl ether. In the polymerization of MMA, the average molecular weight increases with an increase in monomer conversion. On the basis of the kinetic studies of the polymerization of MMA initiated by RhCl(CO)(P(C6H5)3)2 and BPO (the mole ratic [BPO]/[RhCl(CO)(P(C6H5)3)2]) was between 1 and 7, the rate of polymerization, Rp' can be expressed by the following equation:

The overall activation energy for the MMA polymerization was found to be 75,3 kJ/mol within the temperature range of 50 to 80°C. The composition curve of the copolymerization of styrene with MMA using RhCl(CO)(P(C6H5)3)2 and BPO agrees with that of the ordinary radical polymerization. On the basis of these results the initiation mechanism is discussed.
Acceleration effect of acids on the co‐dimer formation from 1‐(4‐chlorophenyl)ethyl esters and styrene
Authors: Kasai Hideaki , Kawabata Hiroshi , Yamaguchi Kazuo , Nakahama Seiichi , Yamazaki Noboru 
Published: April 2003

AbstractA linear unsaturated co‐dimer of styrene and p‐chlorostyrene, 1‐phenyl‐3‐(4‐chlorophenyl)‐1‐butene (2), was preferentially produced by reaction of 1‐(4‐chlorophenyl)ethyl diphenyl phosphate (1) with styrene. The reaction was found to be extraordinarily accelerated by addition of trifluoromethanesulfonic acid. 1‐(4‐chlorophenyl)ethyl acetate reacts readily with styrene in the presence of trifluoromethanesulfonic acid to afford 2 in good yields, whereas the acetate is inert toward styrene in the absence of a super acid.