bluuebunny/crossref_metadata_2025 huggingface dataset:
13C‐NMR‐Sequenzanalyse, 2. Herstellung alternierender, aliphatischer Copolyamide aus Oligoamid‐pentachlorphenylestern
Authors: Kricheldorf Hans R. , Leppert Elmar , Schilling Gerhard
Published: April 2003

Ausgehend von Boc‐Glycin wurden auf bekannte Weise N‐(Boc‐Glycyl)aminocarbonsäure‐pentachlorphenylester 8 und N‐[N‐(Boc‐glycyl)‐aminoacyl]aminocarbonsäure‐pentachlorphenylester 9 hergestellt, deren Boc‐Gruppe mittels Trifluoressigsäure abgespalten wurde. Die resultierenden Trifluoracetate 2 und 3 wurden bei 150°C in N,N‐Dimethylacetamid oder in Imidazol durch Zugabe von N,N′‐Tetramethyläthylendiamin oder N‐Trimethylsilylimidazol als Protonenacceptor polykondensiert. Die so dargestellten Copolyamide haben, wie ihre 13C‐NMR‐Spektren zeigen, eine alternierende Sequenz; denn bei alternierenden Sequenzen liegen die 13C‐Carbonylsignale der verschiedenen Monomerbausteine weiter auseinander als bei einem Gemisch entsprechender Homopolyamide oder bei einem Copolyamid mit homologen Blöcken (“Differenzierungseffekt”). Die chemische Verschiebung der 13C‐Carbonylsignale wird durch die gesamte Sequenz bestimmt, so daß sich mittels der 13C‐NMR‐Spektroskopie im Gegensatz zur 1H‐NMR‐Spektroskopie auch isomere Sequenzen unterscheiden lassen, z. B. …—[Glycyl‐β‐alanyl‐4‐aminobutyryl—]… von …—[Glycyl‐4‐aminobutyryl‐β‐alanyl—]…
Multimerization: Association and aggregation, 14. Distinction between open and closed associations
Authors: Elias Hans‐Georg , Šolc Karel
Published: April 2003

Open and closed molecule‐based associations with experimentally incompletely accessible concentration dependencies of the apparent molecular weights can be distinguished by plotting the apparent weight average molecular weight, (Mw)app, versus the inverse apparent number average molecular weight, (Mn). For closed associations, straight lines are observed for theta‐systems and concave ones for non‐theta‐systems of associating rods. Open associations in these cases give convex lines for both, theta and non‐theta‐systems. Loops can be expected for both types of associations for non‐theta‐systems at high concentrations. A similar plot can be based on apparent z and weight average molecular weights.
Contribution à l'étude de la structure des polytéréphtalates de quelques polyméthylèneglycols
Authors: Joly Adrien M. , Nemoz Guy , Douillard Alain , Vallet Georges
Published: April 2003

L'étude des domaines cristallins au moyen de la diffraction des rayons X de fibres étirées bien cristallisées a montré que les polytéréphtalates d'éthylèneglycol (1a), de butanediol‐1,4 (1b), de pentanediol‐1,5 (1c) et d'hexanediol‐1,6 (1d) cristallisent dans le système triclinique. L'évolution des paramètres ne se fait pas régulièrement en fonction de la longueur du motif monomère. La connaissance du réseau cristallin et de la structure chimique nous a conduit à proposer des conformations permettant aux chaǐnes de s'arranger dans le réseau et de proposer ainsi des hypothèses de structure pour les polyesters étudiés.

Ces résultats sont confirmés par l'examen des spectres IR des échantillons cristallins qui présentent des bandes caractéristiques de conformation trans très importantes pour les polyesters 1a et 1d alors que les polyesters 1b et 1c présentent des bandes de structure gauche importantes. L'étude du taux de cristallinité par différentes méthodes (rayons X, calorimétrie différentielle, spectres IR et colonne à gradient de densité) confirme la valeur proposée pour le volume de la maille du polyester 1d.
Optically active hydrocarbon polymers with aromatic side chains, 7. Synthesis and properties of copolymers of vinyl aromatic monomers with chiral α‐olefins
Authors: Carlini Carlo , Chiellini Emo
Published: April 2003

Optically active alkyl‐α‐olefins such as (R)‐3,7‐dimethyl‐1‐octene (1), (S)‐4‐methyl‐1‐hexene (2), and (S)‐5‐methyl‐1‐heptene (3) were copolymerized with styrene (4), 1‐vinylnaphthalene (5) or 2‐methylstyrene (6) by Ziegler‐Natta catalysts based on VCl4, TiCl4 or TiCl3 “ARA” and Al[CH2CH(CH3)2]3 or Al(C2H5)3.

Fractionation by solvent extraction as well as optical rotation and differential dichroic absorption (Δε) demonstrate unequivocally the formation of copolymer macromolecules. The isotactic enchainment of the units is supported by IR and X‐ray spectra.

A remarkable contribution to optical rotation by aromatic units is observed in the copolymers of 1. In addition circular dichroism data relative to the lowest energy π→π* electronic transition of aromatic nuclei show that aromatic units, when inserted in optically active copolymer macromolecules, assume a preferential chiral conformation.
Synthesis of polyurethanes containing imide groups in the main chain from a mixture of isomeric N,N‐bis(isocyanatotolyl)pyromellitimides and α,ω‐diols
Authors: Matsuda Hideaki
Published: April 2003

The reaction of pyromellitic dianhydride (1) with 2,4‐tolylene diisocyanate (2) was investigated. It was found that N,N′‐bis(isocyanatotolyl)pyromellitimide (3) is formed, which contained three stereoisomers.

Polyurethanes containing imide groups in the main chain were synthesized by a polyaddition reaction of the diimide 3 with α,ω‐diols. The polymers obtained were yellow or yellow brown powders with inherent viscosities (in DMF) of 14–28 cm3/g. DMF, DMSO and m‐cresol were found to be good solvents for these polymers. The results of TG of these polymers were discussed.
Characterization of the structure of the stereocomplex of poly(methyl methacrylate) in solution from NMR relaxation data
Authors: Spěváček Jiří , Schneider Bohdan
Published: April 2003

From the values of relaxation times T2 determined on a pulse spectrometer, and from the shape of bands in high resolution (HR‐) and broad line (BL‐) NMR spectra, two types of protons, different in mobility, were found to exist in the associated stereocomplex of isotactic (it‐) and syndiotactic (st‐) poly(methyl methacrylate) (PMMA). From the analysis of NMR spectra, measured at magic angle rotation (MAR‐NMR), the mobility of the ester groups in the stereocomplex is shown to be greatly hindered. Temperature changes of HR‐NMR spectra of mixed solutions of it‐ and st‐PMMA in benzene indicate that the associated segments of the stereocomplex can be characterized as junctions of a network of nonassociated sequences.
Zum Mechanismus des Abbaus von Polymeren in Lösung durch Ultraschall
Authors: Basedow Arno M. , Ebert Klaus H.
Published: April 2003

Die Abbaureaktion von Dextran durch Ultraschall wurde im Molekulargewichtsbereich von 30 000 bis 90 000 in verschiedenen Lösungsmitteln untersucht. Die Abbauprodukte wurden durch ihre Molekulargewichtsverteilungen, die mit Hilfe von Chromatographie an porösem Glas bestimmt wurden, charakterisiert. Aus den Ergebnissen der Untersuchungen konnte abgeleitet werden, daß die Abbaureaktion nach erster Ordnung verläuft, die Abbaukonstante proportional dem Molekulargewicht ist, und die Moleküle bevorzugt in zwei nahezu gleichgroße Bruchstücke zerfallen. Die Art des Lösungsmittels hat dabei einen erheblichen Einfluß auf die Abbaukonstanten; es wurde gefunden, daß diese der molaren Verdampfungsenthalpie des Lösungsmittels direkt proportional sind. Der Einfluß der Konformation des Polymeren auf die Abbaukonstanten wurde studiert, wobei sich ergab, daß mit einer Aufweitung der Polymerknäuel die Abbaukonstanten größer wurden.

Die Ergebnisse bestätigen die allgemeine Auffassung, daß die Kavitäten, die bei der Ultrabeschallung entstehen, für die Abbaureaktion verantwortlich sind. Eine eindeutige Entscheidung, ob die inhomogenen Strömungsfelder oder die Stoßwellen, die bei der Implosion der Kavitäten entstehen, für den Molekülbruch letztlich maßgebend sind, kann mit den bisher vorliegenden Ergebnissen nicht getroffen werden. Der Befund, daß aufgeweitete Knäuel leichter abgebaut werden, spricht für den Stoßwellenmechanismus. Andererseits wird ein Modell für die Abbaureaktion angegeben, in dem beide Effekte insoweit zusammenwirken, daß die inhomogenen Strömungsfelder das Polymerknäuel zunächst strecken und die nachfolgende Stoßwelle den Molekülbruch bewirkt.
Study by 19F nuclear magnetic resonance spectroscopy of the cationic polymerization of tetrahydrofuran initiated by PF5
Authors: Andruzzi Fulvio , Pescia Aldo , Ceccarelli Giulio
Published: April 2003

By means of 19F‐NMR spectroscopy it was possible to detect and estimate the hexafluorophosphate ion (PF) in the THF polymerization, initiated by PF5 in methylene dichloride at 25°C. The observed variations with time of [PFPF], [PF5·THF], and [PPF] were analysed kinetically, and by means of the resulting equations, the rate constants for initiation, propagation and termination were evaluated. Comparison of our kp value with those of others indicates that our method is sound, and we conclude that it should be applicable to other similar systems.
Flash pyrolysis of poly(propylene) stereoisomers
Authors: Audisio Guido , Bajo Giuseppe
Published: April 2003

Stereoirregular, isotactic, and syndiotactic poly(propylene) were decomposed by the gaschromatographic pyrolysis technique. Some components of the tetramer fraction were identified and resolved into the two possible diastereomers. The relative intensities of these vary according to the tacticity of the decomposed polymer. The hydrogenation is a source of perturbation in the tacticity measurement as well as the partial isomerization.
Evaluation of triads in methyl methacrylate/methacrylic acid copolymers by 1H‐NMR in different solvents and 13C‐NMR
Authors: Klesper Ernst , Johnsen Andreas , Gronski Wolfram , Wehrli Felix W.
Published: April 2003

The probabilities of compositional‐configurational triads in tactic and atactic methyl methacrylate/methacrylic acid copolymers are evaluated. After verification of the assignment of syndiotactic and isotactic triads in the 1H‐NMR spectra of tactic methyl methacrylate/methacrylic acid copolymers in three NMR solvents, the chemical shifts of the heterotactic triads are postulated by shift increments. The postulated assignment of the heterotactic triads is supported by comparison of the experimental 1H‐NMR peak intensities of atactic methyl methacrylate/pentadeuteromethacrylic acid copolymers and atactic pentadeuteromethyl methacrylate/methacrylic acid copolymers in three NMR solvents with calculated triad probabilities. The compositional and configurational parameters needed for the calculation of triad probabilities are determined. It is shown how the peak areas obtained from the two partially deuterated, atactic copolymers in different solvents may be combined to determine the probabilities of all compositional‐configurational triads in atactic copolymers. Possibilities for the evaluation of triad probabilities from the 13C‐NMR spectra of tactic and atactic methyl methacrylate/methacrylic acid copolymers are presented.
Strukturuntersuchungen an Adsorptionsschichten makromolekularer Stoffe, 2. Haftstellenzahlen linearer Polyester an wasserfreien γ‐Aluminiumoxidoberflächen und ihre Beeinflussung durch Poly(oxyäthylen)e und Wasser als Konkurrenzadsorptive
Authors: Joppien Günter Richard
Published: April 2003

Die Struktur der Adsorptionsschichten von linearen, gesättigten, aliphatischen Polyestern, adsorbiert aus Lösung in CCl4an die Oberfläche von wasserfreiem, pyrogenem γ‐Aluminiumoxid, wird durch IR‐spektroskopische Bestimmungen der Bruchteile spezifisch gebundener Kettencarbonylgruppen (Haftstellenzahlen) und der adsorbierten Mengen beschrieben. Durch verschieden starke H‐Brückenbindung der Carbonylgruppen an oberflächenständige Aluminolgruppenpaare und anwenigstens zwei Arten isolierter Alumisolgruppen, die sich durch die Zahl ihrer O2—‐Nachbarn unterscheiden, wird die IR‐Bande der CO‐Valenzschwingung nach drei kleineren Wellenzahlen verschoben. Die energetische Heterogenität der Adsorptionsplätze an der wasserfreien Al2O3‐Oberfläche bewirkt, daß sich nach rasch erfolgender Adsorption die Gleichgewichts‐Schlaufenstrukturen in den Polyesterschichten sehr langsam ausbilden. Die Geschwindigkeit der Langzeit‐Orientierungsprozesse ist von der absorbierten Menge, vom Molekulargewicht der Adsorptive und von der Polyesterstruktur, nicht dagegen von der chemischen Natur der Endgruppen der Polyester abhängig. Mit einer Monoschicht Wasser bedeckte Al2O3‐Oberflächen haben energetisch homogene Adsorptionsplätze, und Polyester‐Gleichgewichtsstrukturen kleiner Schlaufengröße bilden sich daran rasch aus. Coadsorption von Polyäthylenglykolen [Poly(oxyäthylen)en] bewirkt keine Desorption von Polyestermolekeln, sondern ein merkliches Ansteigen der adsorbierten Polymermengen in den sich ausbildenden Mischadsorptionsschichten, die aus großen Adsorptionsschlaufen bestehen. äthergruppen der Polyäther können offenbar gebundene Kettencarbonylgruppen der Polyester nur von Aluminolpaaren und von isolierten Aluminolgruppen ohne O2−‐Nachbarn, nicht dagegen von Aluminolgruppen mit vier oder drei O2−‐Nachbarn verdrängen.
A general method of the synthesis of “step‐ladder” polymers
Authors: Korshak Vasiliy V. , Rusanov Alexander L. , Iremashvili Tsiala G. , Plieva Larisa Kh. , Lekae Tat'yana V.
Published: April 2003

A new general method for the synthesis of “step‐ladder” polymers was developed. It involves the interaction of aromatic diamines, containing in o‐positions aromatic heterocycles with reactive hydrogen atoms, with aromatic dicarboxylic acids or their derivatives. This general method was used for the preparation of new classes of thermally stable polymers of type 27, 28, 29 and 30, containing 1,2,4‐triazole‐, 1,2,4‐triazolo[4,3‐c]‐quinazoline‐, benzimidazole‐ or benzimidazolo[1,2‐c]quinazoline‐rings. Physical properties of these polymers were determined together with those of corresponding model compounds.
Determination of compositional heterogeneity of styrene‐methyl methacrylate block copolymers
Authors: Kotaka Tadao , Uda Taichiro , Tanaka Takeshi , Inagaki Hiroshi
Published: April 2003

Determinations of compositional heterogeneity of anionically prepared block copolymers of styrene (S) and methyl methacrylate (M) were attempted by three different methods: thin‐layer chromatography (TLC), cross‐fractionation, and by a computer simulation method. To this end the TLC elution behavior of diblock and triblock copolymers of SM‐ and MSM‐type were compared with those of their statistical copolymers. A new TLC method was devised which does not require any reference samples as TLC elution standards. The compositional distributions determined by the three methods were in good agreement with one another, and found to be unexpectedly broad. The implication of such a result was discussed on the basis of the polymerization mechanism of the block copolymers.
On the formation of tert‐butyl radicals after irradiation of polymers containing tert‐butoxycarbonylthioethylene units
Authors: Mönig Hans , Ringsdorf Helmut , Wessel Silvia
Published: April 2003

The formation and the behaviour of radiation induced free radicals in poly[1‐(tert‐butoxy carbonylthio)ethylene] (2) and in a statistical copolymer 4 from O‐tert‐butyl S‐vinyl thiocarbonate (1) with N‐vinylpyrrolidone (1:1) was studied, using ESR spectroscopy. After γ‐irradiation at 77 K, tert‐butyl radicals and other species were detected in the polymers. The yield for the homopolymer was evaluated to be Gtert‐butyl = 0.18. Investigations on the behaviour of radicals with an annealing procedure revealed, that at first the tert‐butyl radicals disappear with increasing temperature and that a further warming up leads to a concentration rise of this radical species. A radical cation localized at the carboxy group is assumed as precursor of this reaction. Further reactions are discussed.
Determination of copolymerization parameters in steady state
Authors: Penchev Pencho
Published: April 2003

In the proposed method copolymerization is carried out in an agradient flow reactor where a steady state is established. For the homogenous radical process the following copolymerization equation holds

where r1 and r2 are the reactivity ratios; a0, b0 and a, b are the feed (with index) and steady mole ratios of monomers to an internal standard. Experimentally the relative substance quantities in the reaction system can be measured with the help of gas‐chromatography. It is possible to calculate statistically the most probable values for r1 and r2 as parameters of the linear form of the above equation. As an example the reaction of styrene and methyl methacrylate in toluene initiated by benzoyl peroxides at 100°C was used. The results are r1 =0,582±0,044 and r2 =0,530±0,004; they agree well with literature values.
Single crystals of linear polyesters
Authors: Girolamo M. , Keller A. , Stejny J.
Published: April 2003

The influence of chemical groups regularly spaced along a polymer chain on structure and behaviour of chain folded single crystals was studied on linear aliphatic polyesters with different lengths of repeating unit. Poly(oxytetramethyleneoxysebacoyl) (or polyester 4,10), poly(oxyhexamethyleneoxysebacoyl) (or polyester 6,10), and poly(oxydecamethyleneoxysebacoyl) (or polyester 10,10) single crystals were grown from solution and their structure and annealing behaviour were examined. Chain folded lamellae with two different structures were formed depending on the chemical composition of polyester. Although in both structures the chains are perpendicular to the lamella surface, the ester group planes {00l} are parallel to the lamella surface in polyester 4,10 as opposed to the polyester 10,10 where the ester group planes are inclined.

In spite of the fact that the chain folded lamellae are of about 100Å thick and can accommodate only few crystallographic repeats along, the lamella thickness of all three polyesters increases continuously with crystallization temperature. A picture of chain folded lamellae containing folds of different but quantized lengths mixed in different proportions is proposed in order to explain the continuous increase of lamella thickness.

On annealing, the lamella thickness of polyester 4,10 and 6,10 increases in discrete steps suggesting that a rearrangement of folds leading to a more uniform fold length mixture takes place. In contrast, in polyester 10,10 the lamella thickness increases continuously on annealing which is attributable to the inclination of the ester group planes to the lamellar surface and to the ensuing non‐equivalence of the folds which distinguishes it from the other two polyesters. Some generalizations about fold length changes are being made.
The rôle of organometallic co‐catalysts in catalytic ziegler‐natta systems
Authors: Zakharov Vladimir A. , Bukatov Gennadii D. , Yermakov Yurii I.
Published: April 2003

The influence of triphenylphosphine and organoaluminium additives of various composition on the activity of titanium dichloride in polymerization of ethylene and propene as well as on the structure of the polypropylene obtained is studied. When these additives are introduced into highly active samples of TiCl2, the polymerization rate decreases, whereas the stereospecificity of the catalytic system increases. On the basis of these and earlier data, conclusions are drawn about the composition of active centers and about the role of organometallic cocatalysts in formation of active centers, in chain propagation, and in formation of stereoregular polymer.
Polyanion—polycation interaction, 2
Authors: Ghosh Amit Kumar
Published: April 2003

The interactions of the basic proteins, ribonuclease, γ‐globulin, and lysozyme with the polyanion potassium hyaluronate at varying pH were studied conductometrically and turbidometrically. The effect of a lowering of pH is most marked in the case of the lysozyme/hyaluronate system, but not to that extent in the case of ribonuclease/hyaluronate or γ‐globulin/hyaluronate interactions. This difference is not obvious. This interaction is also dependent on the nature of the polyanion.

Titrations are dependent on the pH of the system not only because of the increasing cationic sites of a protein with lowering of pH, but also due to the simultaneous decrease in the dissociation of the anionic groups of the polyanion; the latter cause is more operative in the weak polyanions like hyaluronate which contain only carboxylate groups.
Hydrophobic environmental effects on oxygenation of polymeric hemochrome in aqueous solution
Authors: Tsuchida Eishun , Honda Kenji , Sata Hiroshi
Published: April 2003

The reversible oxygenation of a synthetic polymeric pyridine‐hemochrome was studied in aqueous solution at room temperature. The polymeric hemochrome was synthesized by coordination of partially quaternized poly(4‐vinylpyridine), (QPVP), to the axial site of protoheme in water. The equilibrium constants of hemichrome and hemochrome were 2,60.102 and 2,77.104dm3 mol−1, respectively, and the coordination number of axial ligands (pyridine groups) both in the complexation of heme and hemin was approximately 1,0.

The kinetics of the elementary processes of oxygenation, i.e. “adsorption of O2” and “irreversible oxidation of the resulting oxygen complex”, were studied as a function of the local field around heme. The rate of the irreversible oxidation process of the heme oxygen complex was greatly lowered as a result of situating the active site of heme inside the hydrophobic environment formed by shrinking QPVP with adding a salt {sodium chloride, sodium dodecylsulfate, and poly[1‐(sodium sulfonatophenyl)‐ethylene]} or by complexing QPVP with poly(methacrylic acid). The redox potential of the central metal ion of heme was lowered by increasing the hydrophobicity around heme. On the other hand, the rate of the adsorption process was approximately constant, regardless of the microenvironmental change around heme.
Studies on polymerizations initiated by syncatalytic systems based on aluminium organic compounds, 2. The interactions of the reactants in the absence of polymerization
Authors: Priola Aldo , Cesca Sebastiano , Ferraris Giuseppe , di Maina Marcello
Published: April 2003

In the course of studies on polymerizations of isobutene (1) by syncatalysts consisting of ethylaluminium halides and halogens, it became necessary to study the separate reactions between the components of the reaction mixtures. The results showed: (a) that in general alkyl chlorides do not react with halogens in the dark at −35°C and below, but do react in the light; (b) that at low temperatures 1 and its dimers react with chlorine more easily by substitution than by addition; (c) that ethylaluminium halides react with halogens by forming aluminium halides, ethyl halides and ethylene.

The findings of the present study enabled us to design polymerization conditions and procedures which minimize undesirable side‐reactions in the polymerization of 1 with syncatalysts.

The experiments with the dimer of 1 (i.e. 2,4,4‐trimethyl‐1‐pentene), which is a non‐polymerizable model compound for 1, supported our view that initiation occurs by a halonium ion.
Studies on polymerizations initiated by syncatalytic systems based on aluminium organic compounds, 3. Polymerization and copolymerization of isobutene initiated by diethylaluminium iodide and iodine
Authors: Giusti Paolo , Priola Aldo , Magagnini Pier Luigi , Narducci Piero
Published: April 2003

The polymerization of isobutene and its copolymerization with isoprene, initiated by diethylaluminium iodide + iodine was studied in pentane, dichloromethane, and chloroethane, and the influence of the concentrations of the reagents and of the temperature on the copolymer yield and molecular weight was investigated. In the homopolymerization of isobutene initiated by diethylaluminium iodide+iodine the initiation is a comparatively slow process leading to non‐stationary reactions. The interaction between initiator and co‐initiator in the absence of monomer produces products (most probably ethylaluminium diiodide) which, on addition of monomer, cause fast, incomplete polymerization of isobutene.
Studies on the hydrolysis reaction of model substances of cellulose in the presence of polymer catalyst, 2. Effect of inorganic salts on the hydrolysis rate of dextrin catalyzed by poly(vinyl alcohol‐co‐vinylsulfonic acid)
Authors: Arai Kenichiro , Ogiwara Yoshitaka
Published: April 2003

The effect of inorganic salts on the hydrolysis rate of dextrin catalyzed by poly(vinyl alcohol‐co‐vinylsulfonic acid) was studied. The reaction is enhanced by addition of sodium chloride and potassium nitrate, and retarded with sodium sulfate and potassium sulfate. It may be presumed that in the presence of large amounts of salts the acidity is a predominant factor for the hydrolysis rate of dextrin in the present system, since it was found that the rate shows a linear relationship with the pH of the reaction mixture, and that the logarithm of the reaction rate was proportional to the ionic strength at values > 0,5 moll−1. The difference in the reaction rates catalyzed by the copolymer or sulfuric acid was diminished with addition of salt, having no relation to whether the reaction rate was enhanced or retarded. Activation parameters of these reactions in the presence of salt were investigated, and it was found that the rate acceleration obtained by addition of salt was due to the increase in entropy of activation, although the enthalpy of activation was also increased. These effects are quite different from that observed in the rate acceleration by introducing hydroxyethyl units into the copolymer, suggesting that the reaction mechanisms for both rate acceleration effects are quite different, as can be inferred from the isokinetic relationships.
Größe und gestalt des fibrinogenmoleküls, 3. Hydrodynamische studien
Authors: Lederer Klaus
Published: April 2003

Hydrodynamische Meßergebnisse (Translationsdiffusionskoeffizient, Rotationsdiffusionskoeffizient, Grenzviskositätszahl) mit verdünnten Lösungen von Fibrinogen vom Rind werden zusammenfassend diskutiert und mit den hydrodynamischen Eigenschaften verschiedener auf elektronenmikroskopischen Ergebnissen beruhender Strukturmodelle verglichen. Die Eigenschaften der Strukturmodelle werden mit Hilfe von hydrodynamischen Modellversuchen ermittelt. Es wird gezeigt, daß die hydrodynamischen Daten nur mit den elektronenmikroskopischen Ergebnissen vereinbar sind, die mit Hilfe der Sprühgefrierätzungsmethode erhalten wurden.
Molecular weight distribution of native poly(D‐β‐hydroxybutyric acid)
Authors: de Mola Argelia Herrera , Marx‐Figini Marianne , Figini Rubén Victor
Published: April 2003

The molecular weight distribution of the biopolyester 1 from D‐β‐hydroxybutyric acid, isolated from Rhizobium meliloti by methods which preserved its native molecular properties, was studied. The weight average degree of polymerization is approximately DPw=23000, 1 being therefore one of the highest biopolymers with respect to chain length. The distribution of the degree of polymerization of 1 is distinguished by a great homogeneity, which it still possesses even after 30 hours of synthesis. One can conclude, therefore, that biosynthesis of an endogeneous bacterial polymer like 1 takes place also by a mechanism which produces molecules of homogeneous chain length, as e.g. a Possion type mechanism, and where the mean time of synthesis coincides approximately with the mean time of generation.
Studies on the aqueous polymerization of acrylamide by the acidified potassium permanganate‐thioglycolic acid redox system
Authors: Husain M. Mukhtar , Gupta Archana , Misra Sadanand
Published: April 2003

The polymerization of acrylamide in aqueous media, initiated by the acidified potassium permanganate/thioglycolic acid (1) redox pair was studied at 30±0,1°C in an inert atmosphere of dry and oxygen‐free nitrogen. The initial rate of polymerization was found to be proportional to nearly the first power of potassium permanganate concentration within the range of 2,0.10−3 to 6,0.10−3 moll−1. The rate was also found to be proportional to the first power of [acrylamide] in the range of 8,0.10−2 to 10,0.10−2 moll−1. The rate of polymerization appears to be independent of thioglycolic acid (1) concentration in the range of 1,0.10−2 to 1,2.10−2moll−1. At still higher concentrations, however, the amount of 1 depresses the rate and maximum conversion. An excess of sulphuric acid was found to affect the rate of polymerization to a slight extent and a deficiency of the acid makes the reaction to stop at an early stage, during the range studied. This indicates, therefore, the presence of an optimum concentration of H2SO4 for the smooth initiation of polymerization.

A study on the effect of salts reveals that KCl and NH4Cl lower the initial rate of polymerization, whereas the reverse is true for MnSO4.H2O and Na2C2O4. The water‐miscible aliphatic alcohols e.g. CH3OH, C2H5OH, (CH3)2CHOH, and C4H9OH were found to depress the extent of polymerization.
Vinyl polymerisation of acrylonitrile initiated by the chromic acid/1,2‐propanediol system in aqueous perchloric acid
Authors: Samal Rajani K. , Singh Baishnab C. , Mohanty Trijama R. , Nayak Padma L.
Published: April 2003

The kinetics of polymerisation of acrylonitrile initiated by the redox system chromic acid/1.2‐propanediol was studied in aqueous perchloric acid at 30–45°C in a nitrogen atmosphere. The rates of polymerisation and the Cr(VI) disappearance etc. were measured. Chromic acid alone did not initiate the polymerisation under deaerated and undeaerated conditions. On the basis of the experimental observation of the dependences of the rate of polymerisation, Rp, the rate of Cr(VI) disappearance, – Rm, etc. on various variables, a suitable kinetic scheme was proposed and various rate and energy parameters were evaluated.
Synthesis and properties of polymers containing 4‐ or 4′‐chalconecarbonyl groups in side chains
Authors: Hatanaka Hideo , Sugiyama Kazuo , Nakaya Tadao , Imoto Minoru
Published: April 2003

Photocrosslinkable polymers containing chalconecarbonyl units were prepared. 2‐Methacryloyloxyethyl 4‐chalconecarboxylate (1) and 2‐methacryloyloxyethyl 4′chalconecarboxylate (2) were synthesized and polymerized by a radical initiator. 1 was copolymerized with methyl methacrylate. The properties of the resulting polymers as photosensitive resins are described.
A radiochemical study of the Ziegler‐Natta catalysed polymerization of styrene
Authors: Ayrey G. , Mazza R. J.
Published: April 2003

The polymerization of styrene in benzene solution was studied at 60°C using a catalyst composed of α‐titanium trichloride and [14C]triethylaluminium. The results obtained showed that the use of this system to measure the number of active sites on the catalyst is an unreliable method likely to over‐estimate the number manifold. Isotope dilution experiments indicated that the contamination was due to the formation of both free and bound [14C]polyethylene. Use of tritiated methanol as a quenching agent to measure active centres indicated that this method yielded results much nearer to the true values. Evidence was also obtained to show that the main reaction governing polymer molecular weight was chain transfer with aluminium alkyl.
Über copolymere der p‐vinylbenzolboronsäure mit styrol
Authors: Hartmann Manfred , Carlsohn Hartmut , Pauls Jörg
Published: April 2003

Die Copolymerisationsparameter der radikalischen Lösungspolymerisation der Systeme p‐Vinylbenzolboronsäure (1a) (M1)/Styrol bzw. p‐Vinylbenzolboronsäure‐bis(trimethylsilyl)‐ester (1b) (M1)/Styrol wurden mit Hilfe von Boranalysen ermittelt:

r1=0,28±0,06 und r2=0,83±0,04

r1=0,28±0,10 und r2=0,87±0,08

Durch Abspaltung der Trimethylsilyl‐Gruppen lassen sich die 1b/Styrol‐Copolymere leicht in 1a/Styrol‐Copolymere überführen. Von einigen Copolymeren wurden Lithium‐, Natrium‐ und Kaliumsalze hergestellt.

Die Lösungsviskositäten der polymeren Boronsäuren in Benzol/Methanol‐Gemischen und in Dimethylsulfoxid (DMSO) hängen deutlich vom Boronsäuregehalt ab. In Benzol/Methanol‐Gemischen kann die Vorzugssolvatation der Boronsäuregruppen durch Methanol nachgewiesen werden. Die Einführung von Boronsäuregruppen in Polystyrol ist mit einem Anstieg der Glasübergangstemperatur verbunden. Torsionsschwingungsmessungen zeigen, daß sich beim Schmelzpressen der Polymeren Vernetzungen ausbilden, bei denen es sich um Boronsäureanhydridstrukturen handelt. Diese Vernetzungen können durch protische Lösungsmittel gespalten werden.
Caractérisation de réactions primaires de dégradation oxydante au cours de l'autoxydation des poly(oxyéthylène)s à 25°C: Étude en solution aqueuse avec amorçage par radiolyse du solvant, 8. Étude cinétique en fonction du ph compris entre 1 et 13
Authors: Crouzet Claude , Decker Christian , Marchal Jean
Published: April 2003

L'emploi de l'amorçage radiochimique a montré que des coupures de chaîne dues à des réactions primaires de dégradation oxydante se produisent au cours de l'autoxydation à 25°C du poly(oxyéthylène) en solution aqueuse. Le changement de 1 à 13 de la valeur du pH des solutions irradiées n'entraîne pas de modification du schéma réactionnel proposé pour rendre compte des résultats obtenus en milieu de pH naturel. Jusqu'à pH 10, la vitesse d'amorcage varie comme le rendement radiochimique GHO. de la radiolyse de l'eau. Au‐delà, cette vitesse diminue jusqu'à devenir nulle vers pH 13.
Gel permeation chromatography: Universal calibration for polypropylene
Authors: Atkinson Carole M. L. , Dietz Roy
Published: April 2003

Twelve well‐characterized fractions of polypropylene and a set of polystyrene standard samples are used to establish the universal calibration in gel permeation chromatography for polypropylene in 1,2‐dichlorobenzene at 135°C. The Mark‐Houwink relation under those conditions and the unperturbed dimensions are determined for polypropylene. Comparisons are made with earlier work with less well characterized samples.
Polymere bis(oxazolo)pyrene. Synthesen und charakterisierung von poly(2,8‐oxazolo[2′,3′:7,8]pyreno[4,5‐d]‐oxazoldiyl‐1,4‐phenylen)en und einigen dazugehörigen modellverbindungen
Authors: Wehr Gregor
Published: April 2003

Durch Reaktion von 4,5,9,10‐Pyrendichinon mit verschiedenen aromatischen Dialdehyden wurden neuartige Polyoxazole synthetisiert. Ihre Struktur wurde durch Vergleich ihrer IR‐Spektren mit denjenigen von entsprechend aufgebauten niedermolekularen Modellsubstanzen bestätigt. Die Thermostabilität der Polymeren wurde untersucht.
Capacity flow method for determination of propagation and termination rate constants in radical polymerization
Authors: Penchev Pencho
Published: April 2003

The possibility of determination of the propagation and termination rate constants kp and kt, resp., as well as their ratios kp/kt and kp/k in homogeneous radical polymerization is shown using the capacity flow method. A theoretical analysis is carried out and relatively simple equations are introduced. The essential point is that the life time of the growing polymer chain is obtained graphically from the residence time of the reactants in the reactor vessel, which is a given quantity. As an experimental example the polymerization of methyl methacrylate initiated by benzoyl peroxide in benzene is investigated in a flow reactor with perfect mixing at 80°C. It is characteristic that the process can be followed by means usually applied for studying slow reactions. The degree of conversion is measured turbidimetrically and gravimetrically, whereas the initiation rate is analysed iodometrically. Thus, through a numerical linear approximation by the method of least squares kp/kt = (2,28±0,45)·10−5, kp/k = (1,50±0,22). 10−1 are found from the experimental data, and hence kp = (9,95±0,83)·102 l mol−1 s−1 and kt = (4,36±0,49)·107 l mol−1 s−1 are obtained.
Copolymères greffés: Poly(méthacrylate d'alkyle‐g‐oxyde d'éthylène), 2. Cristallisation
Authors: Thierry Annette , Skoulios Antoine
Published: April 2003

La cristallisation de greffons poly(oxyéthylène) a été comparée avec celle du poly(oxyéthylène) homopolymère parent.

Les cinétiques de cristallisation, degré de cristallinité, température de fusion, structure et texture ont été étudiés par dilatométrie, diffraction des rayons X, et microscopie en lumière polarisée.

Les greffons cristallisent beaucoup plus lentement que l'homopolymère, et leur structure est beaucoup moins régulière que celle de l'homopolymère parent.
An polyvinylalkoholträgern immobilisierte enzyme
Authors: Manecke Georg , Vogt Hans‐Günter
Published: April 2003

Aus mit Terephthalaldehyd vernetztem Polyvinylalkohol wurden durch Umsetzung mit 2,4,6‐Trichlor‐s‐triazin, 4‐Nitrobenzylchlorid beziehungsweise 2‐(3‐Aminophenyl)‐1,3‐dioxolan und Folgereaktionen reaktive Träger hergestellt, die mit Papain, Trypsin und Glucose‐Oxydase aktive Enzympräparate ergaben.

Das Bindungsvermögen des letztgenannten Trägers für die Enzyme wurde in Abhängigkeit von der zur Immobilisierung eingesetzten Enzymmenge sowie für Papain vom Gehalt an reaktiven Gruppen des Trägers untersucht.

Für die immobilisierten Hydrolasen wurden die Eigenschaften wie Aktivität, pH‐Aktivitäts‐Profil, KM(app.)‐Werte, Lager‐ und Thermostabilität, sowie Stabilität bei wiederholtem Einsatz bestimmt.
Polymerization of styrene, catalyzed by aluminium trichloride in different solvents
Authors: Husain Md. Mukhtar , Gupta Archana
Published: April 2003

The polymerization of styrene, catalyzed by aluminium trichloride, in different polar and non‐polar solvents, e.g. chlorobenzene, nitrobenzene, benzene, toluene, and cyclohexane was studied at 30°C. The polymerization rate at fixed initial amounts of monomer and catalyst is correlated with the dielectric constants and individual natures of the solvents used.
Absolutes molekulargewicht der nativen cellulose der alge valonia
Authors: Palma Alfredo , Büldt Georg , Jovanović Slobodan M.
Published: April 2003

Der Polymerisationsgrad der nativen Cellulose der Alge Valonia wurde bei dem unfraktionierten Material zu Pw≈26500 und bei dem durch Fällungsfraktionierung isolierten hochmolekularen Anteil der Molekulargewichtsverteilung zu Pw≈44000 ermittelt. Diese letzte Größe legt die Dimension fest, die die synthetisierende Matrize geometrisch erfüllen muß. Sie dürfte um einen Faktor von ca. 3 größer sein als die bei der Baumwollcellulose mit Pw≈14000.

In Verbindung mit anderen Untersuchungen wird eine Biosynthese des Cellulosemoleküls als sehr wahrscheinlich angesehen, die direkt auf einer flächenförmigen Matrize zu einer gefalteten Kette führt. Da die thermodynamisch kontrollierte Faltungslänge zu meßbaren aber bei der nativen Cellulose nie beobachteten Perioden in der Faserrichtung fü+en müßte, wird die Hypothese einer «genetisch» kontrollierten Faltungslänge zur Diskussion gestellt. Die Kristallisierung zu dem Gitter der Cellulose I müßte dabei nach der Ablösung des Moleküls vom Synthesezentrum unabhängig von der Faltungslänge erfolgen. Innerhalb dieses Schemas ist eine Elementarfibrille denkbar, die aus einem monomolekularen Band mit der häufig beobachteten Breite von 35 Å und einer Faltungslänge von ca. 104 Å bei der Baumwolle und von ca. 3·104 Å bei der Alge Valonia besteht.
Pressure influence on true cosolvency. Measured and calculated solubility limits of polystyrene in mixtures of acetone and diethylether
Authors: Wolf B. A. , Blaum G.
Published: April 2003

The phenomenon of “true cosolvency”, which has only recently been observed in the system acetone/diethyl ether/polystyrene (AC/DEE/PS), is investigated with regard to its pressure dependence and compared with the thermodynamic behaviour of the corresponding binary sub‐systems. For the determination of the limits of complete solubility, a pressure apparatus was used which had been constructed, in order to measure the turbidity of fluids in the temperature range of −70 to +500°Cand in the pressure range of 1 to 4000 bar (105 to 4·108 Nm−2).

The critical line observed for the system DEE/PS (MPS=20400) looks similar to that reported for AC/PS in the literature, i.e. the upper critical solution temperatures are shifted towards lower and the lower critical solution temperatures towards higher values when the pressure is increased. In the case of true cosolvency (MPS=110000), the critical line for atmospheric pressure encircles the range of temperature and composition of the mixed solvent within which the solutions stay homogeneous irrespective of polymer concentration. With increasing pressure, this range expands all around, thus creating a trumpet‐like surface. This experimental result is well reproduced theoretically by the “single‐liquid approximation” of Scott, where the thermodynamic behaviour of the binary sub‐systems is described on the basis of the Prigogine‐Patterson theory.
Synthesis of polymers containing phosphoric ester
Authors: Kimura Toshio , Nakaya Tadao , Imoto Minoru
Published: April 2003

Benzyl 2‐(methacryloyloxy)ethyl 2′‐(phthalimido)ethyl phosphate (1) and 2‐(methacryloyloxy)ethyl 2′‐(phthalimido)ethyl hydrogen phosphate (3) were synthesized, characterized, and polymerized with 2,2′‐azoisobutyronitrile. The properties of the resultant polymers are described.
Mechanismus der NCA‐Polymerisation, 3. Über die Amin katalysierte Polymerisation von Sarkosin‐NCA und ‐NTA
Authors: Kricheldorf Hans R. , Bösinger Klaus
Published: April 2003

Das bislang unbekannte Sarkosin‐NTA

NCA bzw. NTA bedeuten N‐Carbonsäure (bzw. N‐Thiocarbonsäure)anhydrid.

(6b), das im Gegensatz zum Sarkosin‐NCA (6a) flüssig und destillierbar ist, wurde aus N‐Äthoxythiocarbonylsarkosin (8) hergestellt. Die Polymerisation des NTAs 6b und des NCAs 6a in Pyridin führt zu höheren Polymerisationsgraden P̄n als mit anderen tertiären Aminen, dabei liefert das NTA stets niedrigere Molekulargewichte als das NCA. Die Pyridinkatalyse ergibt beim NTA neben Polysarkosin auch 1,4‐Dimethyl‐2,5‐dioxopiperazin (3a), dessen Anteil mit fallender Monomer‐konzentration zunimmt. Die Polymerisation von Sarkosin‐NCA mit Pyridin und γ‐Picolinhat den steilsten Anstieg von P̄n zwischen 90 und 100% Umsatz, während mit Triäthylamin als Katalysator P̄n in diesem Umsatzbereich wieder abfällt. Verschiedene Reaktionsmechanismen werden diskutiert; im Falle der Pyridinkatalyse ist die Bildung und Polykondensation von „Zwitterionen”︁ der wahrscheinlichste Mechanismus. Das NCA 6a wurde ferner mit tert‐Butylamin bei verschiedenen Monomer/Initiator‐Verhältnissen polymerisiert, P̄n durch 1H‐NMR‐Spektroskopie bestimmt und eine (ηsp/C)/M̄n‐Eichkurve ermittelt.
Stabile Polykohlenstoffradikale, 2. Versuche zur Darstellung von Polyradikalen des Triphenylmethyl‐Typs, verknüpft über p‐Phenylen‐Einheiten
Authors: Braun Dietrich , Lehmann Peter
Published: April 2003

Als Ausgangsverbindungen für die Darstellung von Polyradikalen des Triphenylmethyltyps, die über p‐Phenylen‐Einheiten verknüpft sind, wurden Bis(4‐jodphenyl)phenylmethan (5a) und Bis(4‐jod‐2,5‐dimethylphenyl)phenylmethan (5b) aus den entsprechenden Diaminoverbindungen durch eine Sandmeyer‐Synthese hergestellt, anschließend nach Ullmann zu den entsprechenden polymeren Kohlenwasserstoffen 6a bzw. 6b kondensiert und mit N‐Bromsuccinimid am tert. C‐Atom bromiert. Aus den Poly(4,4′‐biphenylylen‐α‐brombenzyliden)en (7a und 7b) wurden mittels Quecksilber Radikale hergestellt und deren ESR‐Spektren aufgenommen. Dabei entstand aus dem methylsubstituierten Polymeren 7b Poly[(2,2′,5,5′‐tetramethyl‐4,4′‐biphenylylen)‐phenylmethylidin] (3) während sich aus dem unsubstituierten Produkt 7a ein para‐chinoides Polymeres mit Radikaleigenschaften bildete.
Cationic polymerization of siloxanes kinetically controlled oligomerization in hexamethylcyclotrisiloxane – linear dimethylsiloxane systems
Authors: Chojnowski Julian , Šcibiorek Marek
Published: April 2003

The kinetically controlled distribution of linear oligomers in the cationic solution polymerization of hexamethylcyclotrisiloxane (D3) in the presence of hexamethyldisiloxane (MM), octamethyltrisiloxane (MDM), and decamethyltetrasiloxane (MD2M) as molecular chain stoppers was investigated by gas chromatography. At an early stage of the process the distribution was practically unaffected by consecutive reactions involving original stable products of oligomerization, which renders the distribution an important tool in the studies of the mechanism of cationic polymerization of siloxanes. Triple pattern distribution (the excess of every third homologue of the MDnM series) is observed even at nearly full monomer conversion. The distribution of this excess oligomers at low monomer conversion is highly specific as the amounts of each subsequent homologue is decreased by a constant factor. The factor is related to the relative reactivity of the siloxane bonds in the chain stopper and in the monomer. In principle, the results agree with the chain mechanism of polymerization involving kinetic chain transfer to the molecular chain stopper.

Studies of the kinetically controlled distribution of linear oligomers in the oligomerization involving a chain stopper of unsymmetrical structure with respect to the reacting siloxane bond allow to determine the specificity of the combination of stopper fragments with a linear molecule. Low specificity showed by MDM constitutes evidence against the mechanism involving a silicenium ion intermediate.
Synthesis and properties of poly(1,2‐acenaphthenediylidene), a rigid chain polymer. A comparison with its non‐rigid chain analogue
Authors: Schopov Ivan , Kirowa Plumka
Published: April 2003

A rigid chain polyene, poly(1,2‐acenaphthenediylidene) (1), was prepared by self‐condensation of acenaphthenone in polyphosphoric acid. Its properties were compared with those of a non‐rigid chain analog, poly(1,2‐acenaphthylenylene) (2). Electronic spectra indicate small intermolecular interactions both in solution and in solid phase. The polymers exhibit semiconducting and paramagnetic properties, to a higher degree in the case of the rigid chain polymer. Coplanarity with the chain and participation of the naphthalene rings in both polymers were postulated for the realization of the semiconductivity. The polymers show good thermal stabilities, polymer 1 being more stable. The conclusion was made that a bond alternation in the polyene chain really exists and that the chain rigidity improves the semiconductivity, the paramagnetism and the thermal stability of the polymers.
Die synthese reiner oligo[(hydroxy‐5‐nitro‐1,3‐phenylen)methylen]e, verbindungen mit mehreren ortho‐ bzw. para‐nitrophenol‐bausteinen im molekül
Authors: Böhmer Volker , Deveaux Jürgen , Kämmerer Hermann
Published: April 2003

Zur Synthese der Oligo[(hydroxy‐5‐nitro‐1,3‐phenylen)methylen]e dienten chlormethylierte Nitrophenole sowie mono‐ und bischlormethylierte Bis‐ und Tris[(hydroxy‐5‐nitro‐1,3‐phenylen)methylen]e. Die Chlormethylierung erfolgte durch Umsetzung mit Chlormethylmethyläther in Gegenwart von Zinkchlorid. Die Synthese der Oligomeren gelang mit guten Ausbeuten, wenn die chlormethylierten Verbindungen mit stark überschüssigem Nitrophenol und Zinkchlorid als Katalysator kondensiert wurden. Reaktionsbedingungen und unterschiedliche Reaktionsfähigkeiten werden mitgeteilt. Einige Verbindungen wurden in ihrer Struktur bestätigt, indem sie auf zwei voneinander unabhängigen Wegen dargestellt wurden. Damit waren auch die Strukturen jener Verbindungen gesichert, die in eindeutig verlaufender Synthese mit den doppelt dargestellten Verbindungen zusammenhängen. Insgesamt konnten 47 neue Oligo[(hydroxy‐5‐nitro‐1,3‐phenylen)methylen]e synthetisiert werden, darunter 12 Zweikern‐, 20 Dreikern‐, 13 Vierkern‐ und 2 Fünfkernverbindungen.
Polymere ester von säuren des phosphors, 4. Polymerisation des 2‐äthoxy‐2‐oxo‐4,5‐dihydro‐1,3,2‐dioxaphosphorins
Authors: Vogt Walter , Siegfried Robert
Published: April 2003

Die ringöffnende Polymerisation des 2‐Äthoxy‐2‐oxo‐4,5‐dihydro‐1,3,2‐dioxaphosphorins (1) mit Alkoholaten als Initiatoren, ist durch folgende Merkmale gekennzeichnet: (a) Zur Polymerisation sind Temperaturen von über 100°C und Reaktionszeiten von vielen Tagen erforderlich. (b) Es stellt sich ein Polymerisations‐Depolymerisations‐Gleichgewicht ein. Für 125°C liegt der maximale Umsatz bei der Polymerisation in Substanz bei 70%. (c) Die Polymerisationsenthalpie hat den Wert 0±12,6 kJ mol—1 (0±3 kcal mol—1). (d) Es werden nur Oligomere gebildet. Die Ausbeute an Substanz mit Pn > 5 liegt um 3%. Die Oligomeren mit Pn = 1 bis 5 werden durch Dünnschichtchromatographie getrennt und durch Massenspektrometrie charakterisiert.