bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zur Fraktionierung von Polymeren mit entmischenden Flüssigkeiten
Authors: Kuhn Rainer 
Published: April 2003

AbstractMan kann chemisch verschiedene Polymere aus homogener Lösung in einem geeigneten Mischlösungsmittel quantitativ voneinander trennen, wenn die Lösungsmittel bei hohen Temperaturen mischbar sind, aber durch Temperatureniedrigung entmischen.Die neuartige Fraktioniermethode wird mit Hilfe der Löslichkeitsparameter von Polymeren und Lösungsmittelgemischen und an einigen Beispielen mit Hilfe der zweiten Virialkoeffizienten beschrieben.Die Nützlichkeit der Fraktionierung wird gezeigt anhand der in einem einzigen Fraktionierschritt durchgeführten Trennung von ca. 30 verschiedenen Mischungen von Polymeren und Copolymeren inklusive Pfropfcopolymeren nach ihrer chemischen Zusammensetzung. Die Fraktionierung mit entmischenden Flüssigkeiten ist besonders in solchen Fällen nützlich, bei denen andere Fraktioniermethoden, z. B. die Fällungsfraktionierung, keine befriedigenden Ergebnisse liefern.Mit der beschriebenen Fraktioniermethode ist es in speziellen Fällen möglich, dreichemisch verschiedene Polymere oder Oligomere quantitativ voneinander zu trennen.
Polyelektrolyte durch assoziat‐bildung von amylose mit azo‐farbstoffen
Authors: Schulz Rolf C. , Trisnadi Julia A. 
Published: April 2003

AbstractDie Wechselwirkung bestimmter Azofarbstoffe mit Amylose in wäßriger Lösung führt zu starken Änderungen der optischen Drehung (induzierte Cotton‐Effekte) und zu einem Anstieg der spezifischen Viskosität. Amylose verhält sich in Gegenwart von z. B. Kongorot (1) oder Diaminechtrot (2) wie ein Polyelektrolyt. Diese Erscheinungen werden mit der Bildung räumlich geordneter Assoziate zwischen Amylose und Farbstoff‐Molekülen erklärt. Andere Farbstoffe (z. B. Azoblau (3) und Calcon (4)) haben weder Einfluß auf die Viskosität noch auf die chiroptischen Eigenschaften. Offensichtlich fehlen in diesen Fällen die erforderlichen strukturellen Voraussetzungen für die Bildung von Assoziaten. Farbstoffe, die bei Amylose Cotton‐Effekte induzieren und die Viskosität verändern, bilden mit Polyvinylalkohol thermoreversible Gele.
Further evaluation of sequences in methyl methacrylate/methacrylic acid copolymers by 1H‐NMR in different solvents and 13C‐NMR
Authors: Johnsen Andreas , Klesper Ernst , Wirthlin Toni 
Published: April 2003

AbstractThe assignment of configurational pentads‐compositional triads in the 13C‐NMR spectra of atactic methyl methacrylate‐methacrylic acid (MMA‐MAA) copolymers is studied. Based on the known chemical shifts of the pentad‐triad sequences in syndiotactic and isotactic MMA‐MAA copolymers, as well as in atactic PMMA and atactic PMAA, chemical shift increments are derived which allow the postulation of the chemical shifts of the remaining pentad‐triad sequences. The postulated assignment of these sequences is verified by comparison of experimental 13C‐NMR peak intensities of three different types of atactic MMA‐MAA copolymers with calculated peak intensities. Because the experimental peak intensities are composed of more than one pentad‐triad resonance which strongly overlap, and can therefore be measured only as a sum, the three MMA‐MAA copolymers are chosen to possess widely differing compositional statistics at the same P(A). The calculated peak intensities are based on the copolymerization theory for the first type copolymer, which was obtained by radical‐initiated copolymerization. For the second type copolymer, derived by half‐esterification of poly(methacrylic anhydride) with methanol, the compositional‐configurational triad peak intensities are first determined by 1H‐NMR spectra using three different solvents. Some features of the statistics of this type of polymer analogous reaction are set forth, and the opening of the anhydride ring is found to be random. This fact allows the accurate calculation of the probabilities of the pentad‐triad sequences. For the third type copolymer, derived by hydrolysis of atactic PMMA in pyridine/water, a blocklike compositional triad distribution was found, which is—as opposed to the second type copolymer—statistically correlated with the configurational sequences. Only an approximate calculation of the probabilities of the pentad‐triad sequences was carried out. For all three types of copolymers a reasonable agreement between experimental and calculated pentad‐triad peak intensities was found.
Crystallization during polymerization of L‐alanine N‐carboxy anhydride initiated by diamines
Authors: Kōmoto Tadashi , Khair B. M. Abo‐El , Maeda Katsura , Oya Masanao , Kawai Tohru 
Published: April 2003

AbstractPolymerization of L‐alanine N‐carboxy anhydride (4‐methyl‐2,5‐dioxo‐1‐oxa‐3‐azacyclopentane) was carried out in acetonitrile using hexamethylene diamine (HM), ethylene diamine (ED) and bis(4‐aminophenyl) ether (AP) as initiators, in order to investigate the effect of diamines on the crystallization mechanism during polymerization in comparison with that for butylamine already reported.The resultant polymers obtained here had wider molecular weight distributions than those obtained with butylamine, indicating the occlusion of some active growing chain ends into the precipitate during polymerization. The relative width of the molecular weight distribution of the polymers formed in the later stages of the polymerization was larger in the following order as compared among the initiators: HM<ED<AP. The oligomer chains formed in the beginning of the polymerization crystallized into the antiparallel β‐structure and thereafter the β‐helical chains grew from the active sites of the β‐chains. However, it is likely that, in the later stages of the polymerization, the α‐helical chains grew from one of the amino groups of a diamine molecule but most of the other amino groups were inactive, since the ends of the β‐chains were occluded into the precipitate due to the antiparallel nature of the β‐chains precipitated. The morphologies of the resultant polymer crystals were in good agreement with the results obtained from the intrinsic viscosities (molecular weights), conformations, and structures.
Heterogeneous polymerization of L‐alanine N‐carboxy anhydride initiated by amines having primary and tertiary amino groups
Authors: Khair B. M. Abo‐El , Kōmoto Tadashi , Kawai Tohru 
Published: April 2003

AbstractVarious amines such as aniline (A), N,N‐diethyl‐1,3‐propanediamine (DPD), and pamino‐N,N‐diethylaniline (ADA), were used as initiators in the heterogeneous polymerization of L‐alanine N‐carboxy anhydride (L‐alanine NCA), (4‐methyl‐2,5‐dioxo‐1‐oxa‐3‐azacyclopentane). When ADA is used as initiator, the initiation reaction proceeds via normal amine initiation as for primary monoamines. On the other hand, in the polymerization initiated by DPD, the initiation reaction takes place from both the primary and tertiary amino groups of the initiator. In all systems, the propagation proceeds by nucleophilic attack of the amino groups of the growing chains on the C(5) of the L‐alanine NCA ring.The resultant polymers obtained in the case of the initiators A or ADA had wider molecular weight distributions than those from DPD‐initiated polymerization. Oligomers and polymers obtained using DPD as initiator were in the form of β‐and α‐conformations, respectively. However, mixtures of both β‐structure and α‐helix were formed in the polymerization initiated by A or ADA. It is suggested that the number of the growing chain ends occluded in the precipitate is increasing in the following order with respect to the initiator used: DPD<A≈ADA. The morphologies of the resultant polymer crystals were in good agreement with the results from IR and X‐ray analysis.
13C NMR chemical shifts and stereochemical structures in poly(vinyl chloride)
Authors: Ando Isao , Kato Yoshiharu , Nishioka Atsuo 
Published: April 2003

AbstractThe 13C NMR chemical shifts of triad and tetrad configurations in poly(vinyl chloride) have been calculated by the average excitation energy approximation using the CNDO/2 MO method. On the basis of these calculations, both Inoue's and Carman's assignments for the observations of the triad and tetrad configurations have been examined and the partial discrepancy between them ascribed to the solvent effect. Further, the tacticity dependences of the calculated chemical shifts for triad and tetrad configurations are discussed.
Acrylsäure‐popcornpolymere, 2. Oberflächenstruktur der glasigen und der popcorn‐polymeren
Authors: Breitenbach Johann Wolfgang , Kauffmann Harald Friedrich , Zwilling Gunther 
Published: April 2003

AbstractDurch Rasterelektronenmikroskopie werden die charakteristischen Unterschiede der Oberflächenstruktur der durch Polymerisation von Acrylsäure in Substanz und in Mischung mit Wasser erhaltenen Polymertypen—opak, glasig, Popcorn—gezeigt. Diese Unterschiede stehen in Beziehung zum Bildungsmechanismus der Polymeren.
Sedimentation measurements on polystyrene solutions in cyclohexane below the Flory theta temperature
Authors: Pouyet Geneviève , Candau Françoise , Dayantis Jean 
Published: April 2003

AbstractSedimentation measurements have been performed, at different temperatures below the Flory Θ temperature (a) on a series of monodisperse polystyrene samples in cyclohexane solution ranging in molecular weights from 8,5·104 to 1,1·106 and (b) on mixtures of the above samples. For the monodisperse polystyrene solutions it is found that the chain dimensions at the critical temperature are smaller than the unperturbed dimensions. For the solutions of the mixtures, the qualitative properties of the Johnston‐Ogston effect were studied. Furthermore, the measurement of the concentrations of each sample in the mixtures (neglecting the effect of the Johnston‐Ogston effect on the area of the peaks) has shown that the slow species is driven by the fast species, as the latter precipitates.
Cationic polymerization of p‐fluoro‐α‐methylstyrene
Authors: Orhan Erdal H. , Akovali Güneri , Baysal Bahattin M. 
Published: April 2003

AbstractBoron trifluoride diethyl etherate‐initiated polymerization of p‐fluoro‐α‐methylstyrene at −78°C in toluene, toluene/mixture of hexane isomers and toluene/hexane was carried out. Determination of the limiting viscosity numbers and molecular weights of some of the polymeric samples led to the evaluation of the Mark‐Houwink constants for poly[1‐(4‐fluorophenyl)‐1‐methylethylene] at 25°C in benzene. Polymerization in 1,2‐dichloroethane at −15°C showed varying rates in the absence of added water. When the molar ratio of added water to the catalyst was 2,5 reproducible rates were observed. The IR spectrum of low‐moleular weight polymers (obtained at −15°C) contained bands corresponding to unsymmetrically disubstituted end‐groups containing double bonds.
Polymerization of mesomorphic monomers, 2. Bulk polymerization of 4‐(2‐vinyloxyethoxy)benzoic acid
Authors: Tanaka Yoshio , Hitotsuyanagi Mikio , Shimura Yukio , Okada Akira , Sakuraba Hidetaka , Sakata Tokuji 
Published: April 2003

AbstractA new thermotropic liquid crystalline vinyl ether, 4‐(2‐vinyloxyethoxy)benzoic acid (1a), was obtained by hydrolysis of the corresponding methyl ester 1b. The radical bulk polymerization of this acid was carried out at 130–195°C in the solid, the mesomorphic, and the isotropic liquid phases with 2,2′‐azoisobutyronitrile to study the effect of monomer ordering on polymerization rate and polymer properties. No significant effect on the rate of polymerization and the intrinsic viscosity of the products appeared to be associated with the existence of the mesomorphic phases. The rate increased with increasing temperature, i.e., decreasing ordering or enhanced mobility of the monomer. The intrinsic viscosity was 0,06–0,10 dl g−1 in N,N‐dimethylformamide at 30°C. High crystalline polymers were obtained in the solid and the mesomorphic phases, whereas the polymer formed in the isotropic liquid phase was a less crystalline solid.
Studies on chitin, 2. Effect of deacetylation on solubility
Authors: Sannan Takanori , Kurita Keisuke , Iwakura Yoshio 
Published: April 2003

AbstractA reproducible method for obtaining water‐soluble chitin and a relationship between solubility and degree of deacetylation of chitin were studied. It was found that the regenerated chitin isolated at low temperature from an alkali chitin solution left at 25°C for 48 to 77h showed very good solubility in water at 0°C. The degree of deacetylation of an alkaline treated chitin was determined by titration with hydrochloric acid. It increased rapidly to about 75% as the alkaline treatment time increased and began to level off to about 90% and only the regenerated chitin samples with around 50% of deacetylation were found to be soluble in water. The X‐ray diffraction diagrams showed that these were amorphous, although both chitin with lower degree of deacetylation and chitosan had crystallinity. The improved solubility of chitin with about 50% of deacetylation would be attributed to the partial deacetylation which probably brought about the destruction of secondary structure and also the increase of the hydrophilic property on account of the increased number of amino groups.
Interaction between dyes and polyelectrolytes, 2. Structural effect of polyanions on the methylene blue binding
Authors: Shirai Masamitsu , Nagatsuka Tatsuki , Tanaka Makoto 
Published: April 2003

AbstractThe structural effect of polyanions on the binding type of methylene blue (1) was investigated spectrophotometrically. 1 was bound to poly(potassium styrenesulfonate) (PSS) and poly(sodium 4‐vinylphenylsulfate) (SVS) in the dimeric or slightly aggregated form and to poly(sodium vinylsulfonate) (SVF) and poly(potassium vinyl sulfate) (PVS) in the highly aggregated (polymeric) form. It was found that the flexibility of polyanions plays an important rǒle in the aggregation of bound 1 and that the difference between SO and OSO as binding site is not a significant factor.
Organozinc catalyst systems for the copolymerization of carbon dioxide with propylene oxide
Authors: Kuran Witold , Pasynkiewicz Stanisław , Skupińska Jadwiga 
Published: April 2003

AbstractA series of new catalytic systems: (C2H5)2Zn/polyhydric phenols was prepared and their activity in the alternating copolymerization of carbon dioxide with propylene oxide (epoxypropane) was studied. On the basis of the results obtained, the structure of organozinc compounds formed in these systems and also in others described in the literature is proposed and discussed. It is shown that the presence of an internal coordinative bond in the catalyst molecule is responsible for its activity in copolymerization.
Synthèse et caractérisation de copolymères triséquencés de différents méthacrylates d'alkyle
Authors: Seow Pin Kwong , Lingelser Jean‐Paul , Gallot Yves 
Published: April 2003

AbstractTriblock copolymers of different alkyl methacrylates with side chains containing 1 to 12 carbon atoms were synthesized by anionic polymerization in tetrahydrofuran with diphenylmethyl sodium or naphthalene sodium (sodium dihydronaphthylide) as initiators. The polymer samples were fractionated by means of solvent/non‐solvent systems. Gel permeation chromatography (GPC), light scattering, osmometry, and elemental analysis were used to characterize the fractions. The copolymers were found to be free of homopolymers and the polydispersity of molecular weight of the fractions to be very low.
Präzisionsmessungen zur bestimmung spezifischer volumsgrößen von makromolekülen in einem vielkomponentensystem, im besonderen von lysozym und papain in wäßrigen saccharoselösungen
Authors: Schausberger Alois , Pilz Ingrid 
Published: April 2003

AbstractA method was developed, which makes it possible to evaluate in a liquid multicomponent‐system the value of specific volumes of a component, by variation of the density of the solution caused by the variation of the concentration of this component.In particular, in the system H2O‐protein‐sucrose the dependence of the partial specific volume of lysozyme and papain was studied on the concentration of proteins in the range of 0 to 10 wt.‐% and on the concentration of sucrose in the range of 0 to 50 wt.‐%.For both proteins no dependence of the partial specific volume of the protein on the concentration of the protein, but an increase of the partial specific volume with increasing concentration of sucrose could be observed.
Photosensitized polymerization of octyl methacrylate under high pressure
Authors: Yokawa Masaru , Yoshida Junichi , Ogo Yoshiaki 
Published: April 2003

AbstractBy use of the rotating sector technique under high pressure, the changes of the rate constants of propagation and termination in the polymerization of octyl methacrylate, Photosensitized with 1,1′‐azocyclohexane‐1,1′‐dicarbonitrile, were studied at 30°C over a pressure range of 1 to 1000 bar at 250 bar pressure intervals. The effects of pressure on the individual rate constants were determined and the activation volumes of propagation and termination were obtained as −24,7 and 20,8 cm3 mol−1, respectively. The overall activation volume was −19,2 cm3 mol−1. The effects were compared with the results for methyl and butyl methacrylate polymerizations. The increase in the size of the ester groups brought about a diminution in the value of the activation volume for the propagation reaction. The effect of pressure on the termination mechanism was discussed from the view point of the viscosity effect on the diffusion‐controlled termination.
Darstellung von Austauschern mit Kryptanden als Ankergruppen
Authors: Blasius Ewald , Maurer Paul‐Gerhard 
Published: April 2003

AbstractFour exchangers (8, 9, 16, and 17) with cryptate forming anchor‐groups were prepared and their properties were studied. They were synthesized by the reaction of the cryptate formers 6 and 7 with chloromethylated polystyrene or by condensation of the cryptate formers 14 and 15 with formaldehyde or with formaldehyde/phenol. The exchangers were found to be very resistant towards heat and chemical attack. Their capacities for alkali salts amount to 1,0–1,3 mmol per gram of the air‐dried resin.
Vernetzte polymere mit spaltbaren netzbrücken, 4. Untersuchungen zur netzstruktur von copolymeren aus 1,2‐bis(4‐vinylphenyl)‐1,2‐äthandiol und styrol
Authors: Braun Dietrich , Brendlein Wolfgang , Paudjojo Lusiawati 
Published: April 2003

AbstractCross‐linked copolymers from styrene and 1,2‐bis(4‐vinylphenyl)‐1,2‐ethanediol (1) were synthesized. The concentration of the pendent vinyl groups linked to the polymer was determined by means of IR‐spectroscopy as a function of the initial composition, of the total monomer concentration, and of the yield. The values were compared with previously elaborated theoretical calculations. Differences between experiment and theory are presumably due to an inhomogeneous distribution of the pendent vinyl groups in the polymerization system. Measurements of swelling with crosslinked copolymers from styrene and 1 showed, that the specific gel bed volume can be well correlated with the theoretically calculated concentration of cross‐links, if the total monomer concentration and the fraction of cross‐linking component are kept below certain maximum values and if the yield does not exceed 80% significantly.
Polymerizable amphiphiles, 1. Synthesis and proton magnetic resonance studies of [3‐(4‐vinylphenyl)propyl]‐β‐D‐glucopyranoside
Authors: Chung Daniel C. , Kostelnik Robert J. , Elias Hans‐Georg 
Published: April 2003

AbstractThe title compound 2 was synthesized and its micellization in water investigated by proton magnetic resonance at 260 MHz. Chemical shift changes with concentration were observed, the largest change being for the aromatic protons indicating ordered phenylene rings in the micelles. The critical micelle concentration of this compound in D2O at 37°C was found to be approximately 0,010g/cm3.
New catalysts for the oxidative polymerization of 2,6‐dimethylphenol, 1. Copper complex of toluene‐3,4‐dithiol
Authors: Kaneko Masao 
Published: April 2003

AbstractIt was found that a copper complex of toluene‐3,4‐dithiol (Cu‐TDT) catalyzes the oxidative polymerization of 2,6‐dimethylphenol (1), and the catalytic behavior was studied. The activity of the Cu‐TDT is higher than that of the known copper(II)‐pyridine complex. The higher the pyridine content in the solvent mixture pyridine/o‐dichlorobenzene, the higher is the activity of Cu‐TDT. Cu‐TDT loses its activity gradually in pyridine solution, however, about 40% of its activity remains even after 150h. The reasons for the high activity are discussed.
Radical copolymerization of cyclic acetals derived from acrolein, 2. Alternating copolymerization
Authors: Acosta José Luis , Mateo José Luis , Sastre Roberto 
Published: April 2003

AbstractCopolymerizations of 2‐vinyl‐l,3‐dioxane (1a), 5,5‐bis(hydroxymethyl)‐2‐vinyl‐1,3‐dioxane (1b), and 5,5‐dimethyl‐2‐vinyl‐1,3‐dioxane (1c) with maleic anhydride (MA) and N‐vinyl‐2‐pyrrolidone (NVP) were investigated. Copolymerization of the cyclic acetals 1 with MA yielded copolymers with perfectly alternating sequences independent of the initial monomer feed composition. Terpolymerization of 1a, MA, and styrene, also despite of monomer composition, yielded terpolymers with a molar composition of 50% in MA which confirms the participation of transfer complexes in these copolymerizations. The composition of the 1/NVP copolymers (mole fraction) F1(NVP) ≈ 0,6–0,8 also varied little with the feed. The copolymerization rates passed through a maximum when the monomer mixture contained a mole fraction f1 (NVP) of ca. 0,7.
Study of the mechanism of propagation and transfer reactions in the polymerization of olefins by Ziegler‐Natta catalysts, 3. Determination of the rate constants of chain transfer with an organo‐alumimium cocatalyst
Authors: Bukatov Gennadii D. , Chumaevskii Nikolai B. , Zakharov Vladimir A. , Kuznetsova Galina I. , Yermakov Yurii I. 
Published: April 2003

AbstractBy quenching polymerization with tritium‐labelled methanol the total number of the metal‐polymer bonds in the polymerization of ethylene and propylene by Ziegler‐Natta catalysts was determined. Using the propagation rate constants determined by quenching polymerization with 14CO the rate constants of chain transfer with AlEt3 and Al(i‐Bu)3 and the activation energy of chain transfer with AlEt3 were calculated.
Réactions primaires de dégradation oxydante au cours de l'autoxydation du poly(oxytétraméthylène) à 25°C, 1. Caractérisation de la production d'éthylène
Authors: Thomassin Claude , Marchal Jean 
Published: April 2003

AbstractAutoxidation of poly(oxytetramethylene) at 25°C was studied by means of radiation induced initiation of chloroformic solutions of the polymer. It includes primary oxidative degradation reactions characterized by main chain scissions and subsequent formation of ethylene, formate groups, and hemiformal groups.