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  • Polymer and Materials Science  (9,610)
  • 1995-1999  (9,610)
  • 1980-1984
  • 1925-1929
  • 1996  (4,900)
  • 1995  (4,710)
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  • 1995-1999  (9,610)
  • 1980-1984
  • 1925-1929
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  • 1
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von 3-Phenylenbismaleimid auf die Werkstoffeigenschaften von CaCO3 gefüllten Polypropylen-Verbundstoffen wurde untersucht. Die Verarbeitungstemperatur spielte eine entscheidende Rolle bei der Herstellung der Verbundwerkstoffe. Bei Verarbeitungstemperaturen oberhalb der Bismaleimid-Zersetzungstemperatur zeigte die Bismaleimid-Verbindung einen positiven Effekt. Die chemische Zusammensetzung der modifizierten Verbunde wurde mit den mechanischen Eigenschaften korreliert. Basierend auf ESCA-Analysen werden Wechselwirkungen zwischen dem Polymeren und CaCO, diskutiert.
    Notes: The effect of 3-phenylene bismaleimide on the mechanical performance of an inorganic filler-based polypropylene composite was studied. The selection of processing temperature played a significant role in the preparation of such composites. A positive effect of the bismaleimide compound was obtained for a processing temperature above the decomposition temperature of bismaleimide. The chemical composition of the modified composite was correlated to its mechanical strength by experimentation involving a rotatable design. An interaction between polymer and CaCO3 has been proposed based on ESCA analysis.
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  • 2
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 33-48 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Chemische und mechanische Eigenschaften von Zwischenprodukten der PE-Schrumpfschlauch-Produktion wurden bei unterschiedlichen Compound-Zusammensetzungen (PE, ein aromatisches Amin oder Phenolderivat als Antioxidans und in einigen Fällen ein Flammschutzmittel und/oder eine Elastomerkomponente) untersucht.Während der Herstellung, besonders während der durch Elektronenstrahlung initiierten Vernetzung, nimmt die thermooxidative Stabilität des Materials gegenüber der des compoundierten Granulats ab. Das aromatische Amin scheint bei gleicher Zusammensetzung das wirksamere und strahlungsbeständigere Antioxidans im Vergleich zum Phenolderivat zu sein. Die Oxidationsstabilität der hergestellten Schrumpfschläuche wird nicht von der Qualität des eingesetzten PE-Ausgangsgranulats beeinflußt.Durch die Alterung des Materials ändern sich die mechanischen Eigenschaften geringfügig. Die Elastomerzugabe bewirkt keine Änderung von Zugfestigkeit und Reißdehnung. Die Stabilität des Endprodukts ist bei weitem ausreichend, um den Spannungen, die beim Schrumpfen während des Gebrauchs auftreten, standzuhalten. Die gute Zugfestigkeit des Materials wird durch die Alterung ebenfalls nicht beeinträchtigt.Bei der Extrusion des Granulats tritt keine nennenswerte Änderung des Molekulargewichts bzw. der Molekulargewichtsverteilung auf. Durch die Bestrahlung wird das Material vernetzt und zu mehr als 50% unlöslich, und seine thermooxidativen Eigenschaften ändern sich deutlich gegenüber dem ursprünglichen PE und dem daraus compoundierten Material.
    Notes: Some chemical and mechanical properties of intermediate products obtained in the production of PE heat-shrinkable tubes were studied at different compositions of the material containing PE, antioxidant (aromatic amime or phenol) and, in some cases, flame retardant and/or an elastomer.In the course of the production phase, the thermooxidative stability decreases compared to that of compounded granulate. The greatest decrease is caused by irradiation. The aromatic amine seems to be a more effective antioxidant at similar compositions than the phenol derivative, and it shows a better resistance against irradiation. The oxidative stability of the finished shrinkable tubes is not affected by the quality of commercial granulate (initial polyethylene).Mechanical properties change slightly upon ageing, and the introduction of the elastomer did not alter the tensile strength and elongation at break. The remaining stability of the end product was still high enough to bear the stress of shrinking in use, and the good tensile strength of the material did not decrease upon thermal ageing either.In the extrusion of the granulated compound no significant change in the distribution and average molecular weight took place. Irradiation produced more than 50% insoluble fraction and the thermooxidative properties of the crosslinked sample changed significantly compared to the original PE and to the compound prepared from it.
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  • 3
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    Angewandte Makromolekulare Chemie 224 (1995), S. 89-96 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In the present work oxygen index (OI) measurements and thermogravimetric analysis (TG) for a series of polyurethanes based on diols and isocyanate were conducted. It was found that a correlation exists between some of the thermal degradation parameters obtained from TG and OI-values. Analysis of experimental results confirms that the amount of mass loss at 250°C is directly proportional to the OI-value. It was also found that the logarithmic temperatures of maximal decomposition rates are directly proportional to the OI-values.
    Notes: In der vorliegenden Arbeit wurden für eine Serie von Polyurethanen auf der Basis von Diol und Isocyanat der Sauerstoffindex (SI) gemessen und die thermische Zersetzung mittels thermogravimetrischer Analyse (TG) untersucht. Dabei wurde ein Zusammenhang zwischen einigen Parametern der thermischen Zersetzung und den SI-Werten gefunden. Die Auswertung der experimentellen Ergebnisse zeigte, daß die Höhe des Massenverlustes bei 250°C und die SI-Werte direkt proportional zueinander sind. Derselbe Zusammenhang besteht auch zwischen dem Logarithmus der Temperatur bei der maximalen Zersetzungsgeschwindigkeit und den SI-Werten.
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  • 4
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    Angewandte Makromolekulare Chemie 224 (1995), S. 109-114 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(acrylsäre-co-acrylamid) wurde mit Zinkoxid und Kryolith (Na3AlF6) in unterschiedlichen Verhältnissen gemischt und bei Raumtemperatur zu Zahnzementen ausgehärtet. IPDT, Temperaturen bei maximaler Abbaugeschwindigkeit, Aktivierungsenergien und Frequenzfaktoren des thermischen Abbaus der Proben wurden aus thermogravimetrischen Messungen ermittelt. Die Probe mit 20 Gew.-% Kryolith in der Füllstoffmischung ist thermisch sehr stabil.
    Notes: Dental cement compositions made by mixing poly(acrylic acid-co-acrylamide) and mixtures of zinc oxide and cryolite (Na3AIF6) in various proportions of 10-50 wt.-% (w/w) were cured at room temperature. From thermogravimetric analyses of the samples, the integral procedural decomposition temperatures (IPDT), maximum decomposition temperatures, activation energies and frequency factors were evaluated. The cured cement sample containing 20 wt.-% cryolite in the filler mixture is thermally very stable.
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  • 5
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    Angewandte Makromolekulare Chemie 224 (1995), S. 133-144 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die wasserlöslichen aromatischen Diazonium-Doppelsalze p-Diazodiphenylaminchlorid/Zinkchlorid (DZS-1) und p-Diazoanisolchlorid/Zinkchlorid (DZS-2) wurden auf ihre Verwendbarkeit als photobleichbare Farbstoffe in der Kontrastverstärkungslithographie untersucht. Nach Untersuchung der Bleicheigenschaften der hergestellten Salze wurde DZS-1 in wäßrigen Lösungen mit Poly(vinylalkohol) als Kontrastverstärkungssystem eingesetzt. Die thermische Stabilität, der Resistkontrast, die Bestrahlungsparameter und andere Bleicheigenschaften wurden untersucht. Im Vergleich zu einem handelsüblichen i-Linien-Photoresist beträgt das Kontrastverhältnis der DZS-1/PVA CEL-Schicht 1,67.
    Notes: Water soluble aromatic diazonium double salts, p-diazodiphenylamine chloride zinc chloride (DZS-1) and p-diazoanisol chloride zinc chloride (DZS-2), have been evaluated as photobleachable dyes for contrast enhancement lithography. After testing the bleaching characteristics, aqueous solutions of DZS-1 and poly(vinyl alcohol) were used as a contrast enhancement material. Thermal stability, resist contrast, exposure parameters and other bleaching characteristics of the photobleachable membranes were investigated. A. commercial i-line photoresist was used to evaluate the contrast ratio of the DZS-1/PVA CEL layer. The contrast ratio obtained in this investigation is 1.67.
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  • 6
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    Angewandte Makromolekulare Chemie 224 (1995), S. 167-178 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Methylen-4,4′-diphenyldiisocyanat und zwei unterschiedliche Bisoxazoline wurden für Kopplungsreaktionen in mit Carboxygruppen terminierten flüssigkristallinen Poly(ethylenterephthalat-co-oxybenzoat)en eingesetzt. Um definierte Bedingungen zu gewährleisten, erfolgte die Synthese von Copolyestern mit unterschiedlichen Carboxygruppenkonzentrationen. Die Bestimmung des Carboxygruppengehalts wird beschrieben.Es erfolgt ein Vergleich des Kopplungsverhaltens beider Arten von Kettenverlängerern. Es konnte nachgewiesen werde, daß die Bisoxazoline bedeutend schneller reagieren als das Diisocyanat. Durch einen geringen Überschuß and Bisoxazolin in der Reaktionsmischung konnte einer thermischen Schädigung vorgebeugt werden. Abhängig von der Menge an zugegebenem Koppler wurden bei den modifizierten Copolyestern Oxazolinendgruppen beobachtet. Außerdem werden mögliche Vernetzungsreaktionen und die thermische Stabilität diskutiert.
    Notes: Methylene-4,4′-diphenyldiisocyanate and two different bisoxazolines were used for coupling reactions in carboxy-terminated liquid crystalline poly(ethylene terephthalate-co-oxybenzoate). In order to guarantee defined conditions, copolyesters with different carboxylic group concentrations were synthesized. The determination of the carboxylic group content is described.The coupling behaviour of both types of chain extenders has been compared. It was evidenced that the bisoxazolines reacted significantly faster than the diisocyanate. A slight excess of bisoxazoline in the reaction mixture prevented thermomechanical degradation. Depending on the amount of coupling agent added, an oxazoline termination of the copolyester was observed. Additionally, probable crosslinking reactions and the thermal stability have been discussed.
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  • 7
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    Angewandte Makromolekulare Chemie 224 (1995), S. 201-201 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 8
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    Angewandte Makromolekulare Chemie 225 (1995), S. 11-20 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von 3-Phenylenbismaleimid auf die Werkstoffeigenschaften von mit Talkum und Zeolith gefüllten Polypropylen-Verbundstoffen wurde untersucht. Durch geeignete Planung des Aufbaus kann die Produkteigenschaft optimiert werden. Die Kapazität zur Füllstoffaufnahme schwankt bei Polypropylen je nach Art des Füllstoffs. Ein hochbelastbarer Verbundstoff kann aus einem geeignet modifizierten, mit Zeolith gefüllten Polypropylen hergestellt werden, auch wenn der Füllstoff in der Verbundmatrix dominiert. Als Ursache dieser Verstärkung wird eine verbesserte Wechselwirkung zwischen dem Polymeren und dem Füllstoff angenommen.
    Notes: The effect of 3-phenylene bismaleimide as a modifier for talc and zeolite-filled polypropylene composites has been studied. The usefulness of the experimental design to assure best product properties has also been illustrated. Polypropylene shows a variable degree of filling capacity depending on the type of filler. A high-strength composite can be prepared with suitably modified zeolite-filled polypropylene even if filler is the dominant phase in the composite matrix. An improved interfacial interaction between polypropylene and filler is proposed to be the reason for this improvement of strength.
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  • 9
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    Angewandte Makromolekulare Chemie 225 (1995), S. 51-61 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die katalytische Oligomerisation von 1-Decen wurde mit Komplexverbindungen mehrerer Übergangsmetalle (Co(II), Co(III), Zr(IV), Ti(IV), Cr(III), V(V)) und Alkyl-aluminiumhalogeniden als Cokatalysatoren durchgeführt. Mit einem Chrom(III)-Et3Al2Cl3-Katalysatorsystem konnten Dimere (C20), Trimere (C30) und Tetramere (C40) von 1-Decen erhalten werden. Die kinematischen Viskositäten und Fließpunkte der hydrierten Oligomere wurden bestimmt und mit den Werten handelsüblicher Proben verglichen. Ein Mechanismus für die Oligomerisation von 1-Decen mit diesem Katalysatorsystem wird vorgeschlagen.
    Notes: The catalytic oligomerization of 1-decene has been carried out employing several transition metal complexes of Co(II), Co(III), Zr(IV), Ti(IV), Cr(III), V(V) in combination with alkyl aluminum halides as cocatalysts. The chromium(III)-Et3Al2Cl3 system exhibits good oligomerizing activity yielding dimers (C20), trimers (C30) and tetramers (C40) of 1-decene. The kinematic viscosities and pour points of hydrogenated oligomers have been determined and compared with those of commercial samples. The probable mechanism of oligomerization of 1-decene on this catalyst is described.
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  • 10
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    Angewandte Makromolekulare Chemie 225 (1995), S. 99-107 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Single-component formulations of epoxy resins with reactive accelerators must be storable. The preparation of several blocked accelerators is described. The basicity of tertiary amines, which correlates with accelerating effects, as well as acidity and structure of polyphenols and modified novolacs influences the extend of blocking. The curing process was investigated by measurements of gel time and viscosity.
    Notes: Einkomponentige Epoxidharzsysteme mit effizienten Reaktionsbeschleunigern müssen lagerstabil sein. Daher wurden Versuche unternommen, Beschleuniger auf Basis von tertiären Aminen mit modifizierten Phenolnovolaken zu blockieren. Das Ausmaß der Blockierung ist sowohl von der Basizität der Amine, die mit der beschleunigenden Wirkung korreliert, als auch von der Acidität und dem strukturellen Aufbau der modifizierten Phenole abhängig. Die Bewertung der Härtungseigenschaften erfolgte über Gelzeitbestimmungen und Viskositätsmessungen.
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  • 11
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Bruchzähigkeit von Phenolphthalein-Poly(etherketon) bei 190°C wurde mit zwei verschiedenen Methoden bestimmt, der konventionellen Rißwachstumsmethode und der „stress whitening zone“-Methode. Die gute Übereinstimmung der Ergebnisse zeigt, daß letztere Methode zur Bestimmung der Rißinitiierung einiger Polymerer herangezogen werden kann, für die das „blunting line concept“ nicht geeeignet ist.
    Notes: Fracture toughness values of phenolphthalein poly(ether ketone) (PEK-C) at 190°C were determined by two different methods, i.e. the conventional crack growth method and the crack stress whitening zone method, which show consistent results. This indicates that the crack stress whitening zone method can be used to determine the crack initiation of some polymers for which the blunting line concept is unsuitable.
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  • 12
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    Angewandte Makromolekulare Chemie 226 (1995), S. 13-22 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Stabilitätskonstanten und zugehörige thermodynamische Parameter (ΔH°, ΔS°) eines intermakromolekularen Komplexes aus Poly(acrylsäure-co-acrylamid), Poly(methacrylsäure-co-acrylamide) und Poly(N-vinylpyrrolidon) wurden mit bekannten Methoden bei verschiedenen Temperaturen bestimmt. Dabei wurde eine stufenweise Auflösung des Komplexes in Abhängigkeit von der Temperatur beobachtet, die mit den Stabilitätskonstanten und den thermodynamischen Parametern korreliert wurde.
    Notes: Stability constant and related thermodynamic parameters (ΔH° and ΔS°) of a multicomponent intermacromolecular complex consisting of poly(acrylic acid-coacrylamide), poly(methacrylic acid-co-acrylamide) and poly(N-vinylpyrrolidone) have been determined using known methods. A distinct stepwise disintegration of the complex at different temperatures has been observed, and this could be correlated with the stability constant and thermodynamic parameters calculated at various temperatures.
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  • 13
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    Angewandte Makromolekulare Chemie 226 (1995), S. 53-57 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von Ultraschall auf die Polymerisation und Depolymerisation von Ethylmethacrylat und der Mechanismus des Kettenabbruchs wurden untersucht. Der Polymerisationsumsatz war unabhängig von den verwendeten Ultraschallbedingungen (800 W, 35 kHz). Depolymerisationsversuche mit Ultraschall bei 20°C zeigten, daß Kettenabbruch im wesentlichen durch Disproportionierung stattfindet; dabei werden Molekulargewichte nicht unter ca. 500000 erreicht.
    Notes: The effect of ultrasound in ethyl methacrylate polymerization and depolymerization and the chain termination mechanism for ethyl methacrylate have been studied. Polymerization conversion at 60°C did not depend on energy (80 W) and frequency (35 kHz) of ultrasound applied. In ultrasound depolymerization studies at 20°C the governing termination mechanism was found to be disproportionation and the lower limiting molecular weight was Mn = 500 000.
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  • 14
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    Angewandte Makromolekulare Chemie 226 (1995), S. 71-87 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The copolymerization of acrylonitrile with maleic anhydride was investigated to synthesize acylic reactive polymers for manufacture of membranes that serve as support for covalent enzyme immobilization. The free-radical copolymer synthesis was carried out in solution (N,N-dimethylformamide (DMF), dimethylacetamide (DMAC), γ-butyrolactone, ethylene carbonate), by precipitation polymerization (dioxane) as well as bulk polymerization. The polymers were characterized using IR spectroscopy, elementary analysis, NMR spectroscopy, gel permeation chromatography, viscosity measurements, osmometry and potentiometry.The kinetic parameters were followed by dilatometric measurements up to high conversions. The anhydride content in the monomer mixtures showed a significant influence on the rate of polymerization and the molecular weight. With raised concentration of anhydride the polymerization rate and molecular weights decreased. Film forming polymers (M̄η 〉 30 000 g/mol) can be obtained by all copolymerization procedures with exception of solution polymerization in DMF and DMAC, respectively. The content of maleic anhydride in the membrane polymers did not exceed 5 mol-%, even though the maleic anhydride content in the monomer mixtures was raised up to the equimolar mixture. Nevertheless, such low maleic anhydride content of prepared membranes is enough for successful enzyme immobilization with amyloglucosidase (copolymer was prepared in γ-butyrolactone, M̄η = 49 000 g/mol, cPMSA = 0,3 mol-%).
    Notes: Die Copolymerisation des Acrylnitrils mit Maleinsäureanhydrid (MSA) wurde mit dem Ziel untersucht, acylfunktionalisierte Reaktivpolymere mit Filmbildungseigenschaften herzustellen, um diese in der Anwendung als Membran für kovalente Enzymfixierungen zu nutzen. Die radikalinitiierte Synthese der Copolymeren wurde in Lösung (Dimethylformamid (DMF), Dimethylacetamid (DMAC), γ-Butyrolacton, Ethylencarbonat), durch Fällungscopolymerisation (Dioxan) sowie in Substanz durchgeführt.Die Polymercharakterisierung erfolgte durch IR-Spektroskopie, Elementaranalyse, Kernresonanzspektroskopie, Gelpermeationschromatographie, Viskosimetrie, Osmometrie und Potentiometrie.Die Kinetik wurde durch dilatometrische Untersuchungen bis zu hohen Umsätzen verfolgt. Danach weist der Anhydridgehalt im Monomergemisch einen signifikanten Einfluß auf die Bruttopolymerisationsgeschwindigkeit und die Molmasse der Polymeren auf. Mit steigendem Anhydridanteil wird die Bruttopolymerisationsgeschwindigkeit herabgesetzt und eine Verringerung der Molmasse herbeigeführt. Die Copolymerisation von Acrylnitril und Maleinsäureanhydrid führt mit Ausnahme der Lösungspolymerisation in DMF bzw. DMAC zu Polymeren mit Molmassen oberhalb 30 000 g/mol, was ihre Anwendung als Membran ermöglicht. Die Einbaurate an Maleinsäureanhydrid in den Membranpolymeren ist bis einschließlich einer äquimolaren Zusammensetzung des Monomergemischs nicht größer als 5 mol-%. Derartig niedrige MSA-Reaktivgruppenanteile erweisen sich jedoch als ausreichend, um an einer aus einem Lösungspolymerisat (γ-Butyrolacton, M̄η = 49 000 g/mol, cPMSA = 0,3 mol-%) formierten Membran eine Enzymimmobilisierung mit Amyloglucosidase nachzuweisen.
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  • 15
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    Angewandte Makromolekulare Chemie 226 (1995), S. 143-160 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Synthesen einer Aryl-alkyl-azodiisocyanat-Verbindung und einer Azoharnstoff-Modellsubstanz werden beschrieben. Aus dem Azodiisocyanat wurden durch Grenzflächen-Polyaddition neuartige Azoharnstoff-Polymer hergestellt. Die zahlenmittleren Molekulargewichte, bestimmt mit der Gelpermeationschromatographie (GPC), lagen zwischen 6000 und 9000. Die Photolyse- und Thermolysereaktionen der Modellsubstanzen und der Polymeren wurden mittels UV-Spektroskopie und Differentialkalorimetrie (DSC) verfolgt und mit den Ergebnissen von ähnlichen Azoamiden verglichen. Der photochemische Polymerabbau wurde mittels GPC untersucht.
    Notes: The synthesis of an aryl alkyl azo diisocyanate and a model azo urea is described. From the azo diisocyanate new azo polyureas were created by interfacial polyaddition. Molecular weights Mn in the range of 6000 to 9000 were determined by gel permeation chromatography (GPC). Photolysis and thermolysis of both, model compounds and polymers, were studied by UV-spectroscopy and differential scanning calorimetry (DSC), respectively, and the results were compared with those of similar azo amides. Photochemical polymer degradation was followed by GPC.
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  • 16
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    Angewandte Makromolekulare Chemie 226 (1995), S. 219-219 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 17
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    Angewandte Makromolekulare Chemie 227 (1995), S. 69-85 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Thermotrop flüssigkristalline Copolyester aus Vanillinsäure (V), 4-Hydroxybenzoesäure (B) und Polyethylenterephthalat (E) wurden mittels 1H-NMR-Spektroskopie und Gelpermeationschromatographie (GPC) untersucht. Die neun möglichen Diaden konnten detektiert und zugeordnet werden. Die Abfolge der Grundeinheiten der V/B/E-Copolyester ändert sich mit zunehmendem B-Anteil von statistischer Verteilung zur Blockbildung und ist außerdem geringfügig von der Katalysatorkonzentration und der Polykondensationsdauer abhängig. Die GPC-Ergebnisse deuten darauf hin, daß die V/B/E-Copolyester engere Molekulargewichtsverteilungen aufweisen als die B/E-Copolyester. Mit von 0 bis 5 mol-% steigendem V-Anteil verengt sich die Molekulargewichtsverteilung. Die Gelpermeationschromatogramme der meisten V/B/E-Copolyester weisen im Unterschied zu den Einzelsignalen der B/E-Copolyester Dublett-Peaks auf.
    Notes: Thermotropic liquid-crystalline copolyesters made from vanillic acid (V), 4-hydroxybenzoic acid (B) and poly(ethylene terephthalate) (E) were examined by 1H-NMR and GPC investigations. Nine possible diads could be identified and assigned. The sequence distribution of V/B/E copolyesters tends to change from random to block with an increase of B content in the copolyesters. The sequence distribution also varies slightly with catalyst concentration and polycondensation time. GPC results suggest that the V/B/E copolyesters have narrower molecular weight distribution (MWD) than B/E copolyesters. The MWD of the copolyesters narrows gradually with increasing V content from zero to 5 mol-%. The GPC chromatograms of the most V/B/E copolyesters show double peaks, which is different from the single peak of the GPC chromatograms of the B/E copolyesters.
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  • 18
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    Angewandte Makromolekulare Chemie 227 (1995), S. 111-120 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Strahlungsbeständigkeit von vorbestrahltem Polypropylen mit 2,5 Gew.-% Ethylenanteil wurde mitr einem Copolymeren aus Polypropylen und einem nukleierenden Agens im Hinblick auf die Strahlungssterilisation von medizinischen Geräten verglichen. Die Transparenz des Propylen-Ethylen-Copolymeren wurde durch die Vorbehandlung verbessert. Im Vergleich mit der ebenfalls verbesserten Transparenz des Copolymeren aus Polypropylen und dem nukleierenden Agens wurde durch die Vorbestrahlung die Strahlungsbeständigkeit während der Bestrahlung und bei der Lagerung des bestrahlten Materials verbessert. Dies wird auf die geringere Kristallinität des vorbestrahlten Polypropylens aufgrund von bei der Bestrahlung gebildeten Verzweigungen zurückgeführt.
    Notes: The radiation stability of the pre-irradiated copolymer of polypropylene containing 2.5 wt.-% ethylene units is compared with a copolymer of polypropylene with a nucleating agent with regard to radiation sterilization of medical devices. It is found that transparency property of the propylene-ethylene copolymer is improved through pre-irradiation processes. This finding was compared with the co-polypropylene with nucleating agent which also gives a better transparency property. In comparison, it is found that pre-irradiated copolymer exhibits better radiation stability during irradiation and during storage after irradiation. The radiation stability of the pre-irradiated copolymer is due to its lower crystallinity caused by the formation of branches during the pre-irradiation process.
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  • 19
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    Angewandte Makromolekulare Chemie 227 (1995), S. 193-193 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 20
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polydiaryldiazosulfide wurden durch Grenzflächenpolykondensation aus aromatischen Bisdiazoniumionen und Benzol-1,3-dithiol erhalten. Auf diese Weise wurden Molekulargewichte Mn von 3400 bis 11700 erreicht (GPC).Die neue Polymerklasse zeichnet sich durch hohe Photolabilität und relativ geringe Thermostabilität aus. Mittels UV-Spektroskopie wurde die Photolyse von Modellver-bindungen und Polymeren verfolgt, wobei in nahezu allen Fällen ein Zerfall 1. Ordnung beobachtet wurde. Der photochemische Kettenabbau konnte durch GPC-Untersuchungen verfolgt werden. Die thermische Stabilität der polymeren Diazosulfide wurde durch DSC-Messungen untersucht.
    Notes: Poly(diaryl diazosulfide)s were synthesized from aromatic bisdiazonium ions and benzene-1,3-dithiol via interfacial polycondensation. Number-average molecular weights Mn in the range of 3400 to 11700 were determined by gel permeation chromatography (GPC).The new polymer class is distinguished by high photosensitivity and low thermostability. First order kinetics during photolysis of nearly all polymers and model compounds under investigation was observed by means of UV spectroscopy. Polymer degradation upon irradiation was verified by GPC measurements. Thermal decay was followed by differential scanning calorimetry (DSC).
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  • 21
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Three different titration methods were proved with respect to accuracy, reproducibility and handling for the determination of maleic anhydride (MSA) content in acrylonitrile (AN) copolymers in form of poly(AN-co-MSA) and poly(AN-co-styrene-co-MSA). The comparison comprises (i) the combined method A/H characterized by the reaction of anhydride groups (AG) with aniline and titration of the formed monoacid with methanolic KOH (A) and the complete hydrolysis of AG and titration of acid groups (SG) with aqueous NaOH (H), (ii) method B based on the conversion of AG with n-butylamine (BA) and back-titration of unreacted amine with HClO4 in glacial acetic acid and (iii) method C consisting of the reaction of AG with p-chloroaniline (pCA) followed by Cl-determination after the Schöniger-decomposition. Whereas all mentioned methods are suitable for the determination of AG in the presence of initial SG, the combination of A/H additionally allows the simultaneous determination of AG and SG. In comparison with the other methods the combination of A/H is to be favoured due to the possibility to obtain additional information about SG and because of the better results in accuracy, reproducibility and handling. By means of FTIR spectroscopy the content of AG and SG was estimated qualitatively and a correlation between the spectroscopic and potentiometric data of AG was discovered.
    Notes: Zur Bestimmung des Maleinsäreanhydrid(MSA)-Gehaltes in Acrylnitril(AN)-Copolymeren des Typs Poly(AN-co-MSA) bzw. Poly(AN-co-Styrol-co-MSA) wurden drei verschiedene Titrationsmethoden hinsichtlich ihrer Richtigkeit, Reproduzierbarkeit sowie ihres Zeitaufwandes geprüft. Miteinander verglichen wurden (i) eine Methodenkombination A/H bestehend aus dem Teilschritt A, einer Umsetzung der Anhydridgruppen (AG) mit Anilin einschließlich der Titration der Monosäuregruppen mit methanolischer KOH, und dem Teilschritt H, einer vollständigen Hydrolyse der AG und Titration der Säuregruppen (SG) mit wäßriger NaOH, (ii) Methode B basierend auf der Reaktion der AG mit n-Butylamin (BA) und der Rücktitration des nicht umgesetzten Amins mit Perchlorsäure (HClO4) in Eisessig und (iii) Methode C, beruhend auf der Umsetzung der AG mit p-Chloranilin (pCA) und nachfolgender Chlorbestimmung durch Schöniger-Aufschluß. Während sich alle genannten Methoden prinzipiell für die AG-Bestimmung in Gegenwart initialer SG empfehlen, ist darüber hinaus über A/H eine simultane Bestimmung von AG und SG möglich. Wegen dieses zusätzlichen Informationsgewinns, ihrer besseren Reproduzierbarkeit, der erhöhten Richtigkeit sowie des geringeren zeitlichen und apparativen Aufwandes ist die Kombination A/H zu favorisieren. Mit Hilfe der FTIR-Spektroskopie wurde der Gehalt an AG und SG qualitativ verfolgt und eine Korrelation zwischen den Bandenintensitäten der AG und den potentiometrisch erhaltenen Werten gefunden.
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  • 22
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    Angewandte Makromolekulare Chemie 229 (1995), S. 15-27 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Härtung eines ungesättigten Polyesterharzes mit niedrigem Exotherm-Peak wurde mit der Standardmethodik und der Differential-Kalorimetrie (DSC) untersucht. Ein Kupfersalz und α-Methylstyrol wurden als Polymerisationsverzögerer benutzt. Der Einfluß der Verzögerer auf die Temperatur des exothermen Peaks, die Gelzeit, die Härtungsenthalpie und die Polymerisationskinetik wurden untersucht.
    Notes: The curing behavior of an unsaturated polyester resin with low exotherm peak was studied by a standard procedure and by differential scanning calorimetry (DSC). A copper salt and α-methylstyrene were used as the polymerization retarders. The influence of the retarders on the exotherm peak temperature, gelation time, exothermic heat and the polymerization kinetics was investigated.
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  • 23
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    Angewandte Makromolekulare Chemie 229 (1995), S. 93-112 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Propen und 1-Octen wurden mit dem syndiospezifischen Metallocen-Katalysator Me2C(Cp)(Flu)ZrCl2/MAO copolymerisiert. Es wurde ein hoher, statistischer Octeneinbau beobachtet. Niedrige Octenkonzentrationen beeinflußten die Aktivität des Katalysators nur wenig; Molekulargewicht, Kristallinität, E-Modul und Glastemperatur wurden dagegen mit ansteigendem Octengehalt erniedrigt. Blends aus ataktischem Oligopropen und syndiotaktischem Polypropen bzw. Poly(propen-co-octen) wurden aus einer Toluol-Lösung hergestellt. Diese Lösungsblends wurden mit einem Reaktorblend verglichen, der mit einem Hybrid-Katalysator bestehend aus einer Mischung von syndiospezifischem Me2C(Cp)(Flu)ZrCl2/MAO und unspezifischem Cp2ZrCl2/MAO hergestellt wurde. Das ataktische Oligopropen wirkte als Weichmacher, der E-Modul und Glastemperatur der Blends erniedrigte.
    Notes: Propene and 1-octene were copolymerized with the syndiospecific homogeneous metallocene catalyst Me2C(Cp)(Flu)ZrCl2/MAO. Large amounts of octene were incorporated randomly. While catalyst activity was not affected markedly by low octene content, molecular weight, crystallinity, Young's modulus, and glass transition temperature were reduced with increasing octene content. Blends of atactic oligopropene with syndiotactic polypropene and poly(propene-co-octene) were prepared from toluene solution and compared with a reactor blend prepared with a hybrid catalyst containing a mixture of syndiospecific Me2C(Cp)(Flu)ZrCl2/MAO and non-specific Cp2ZrCl2/MAO. Atactic oligopropene acted as plasticizer reducing Young's modulus and glass transition temperature of the blends.
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  • 24
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    Angewandte Makromolekulare Chemie 229 (1995), S. 175-184 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die innere Oberfläche und das Hohlraumsystem von verschiedenartigen Celluloseregeneratfasern werden mit Röntgenkleinwinkelstreuung untersucht. Dabei wird gefunden, daß alle Fasern ein Hohlraumsystem von 0,01 bis 0,1% (Volumenanteil 10-4-10-3) aufweisen. Es zeigt sich jedoch, daß die Größe des Hohlraumsystems für die mechanischen Eigenschaften wenig Bedeutung hat. Es ist vielmehr die Gestalt der Hohlräume und ihre Orientierung, die hier wesentlich sind. Es wird gefunden, daß langgestreckte Hohlräume, vermutlich orientiert, für gute mechanische Eigenschaften verantwortlich sind. Damit können auch verbesserte textile Eigenschaften von Lyocellfasern des NMMO-Typs erklärt werden.
    Notes: Both the inner surface and the void system of different cellulose regenerate fibers are investigated with X-ray small angle scattering. Thereby it turns out that all fibers have a void system of 0.01 to 0.1% (volume fraction 10-4-10-3). However, the amount of the void system has little influence on the mechanical properties. Rather, it is the shape of the voids and their orientation which proves essential. It is found that elongated voids, probably well oriented, are responsible for superior mechanical properties. This explains also improved textile properties of lyocell fibers of the NMMO type.
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  • 25
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    Angewandte Makromolekulare Chemie 230 (1995), S. 1-12 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die mit γ-Strahlen induzierte Polymerisation von Methacrylsäure (MA) und Acrylsäure (AA) mit Acrylamid (AAm) (M2) in Substanz wurde untersucht. Die nach Kelen-Tüdős berechneten Copolymerisationsparameter betragen r1 = 1.35 und r2 = 0.22 für MA-AAm bzw. r1 = 1.75 und r2 = 0.10 für AA-AAm. Die Polymerisationsgeschwindigkeit hängt sowohl von der Temperatur als auch von der Comonomerzusammensetzung ab. Die differentialkinetischen Kurven sind unimodal, was darauf hinweist, daß nur der Copolymerisationsprozeß abläuft. Ein zweites Maximum in diesen Kurven wird mit Vernetzung und der Bildung wasserunlöslicher Bestandteile erklärt. Die Copolymeren sind weiße Pulver; die wasserlöslichen Fraktionen sind im Gegensatz zu den wasserunlöslichen nicht giftig, aber als Immunmodulatoren weniger aktiv.
    Notes: A study was made of the γ-radiation-induced bulk copolymerization of the methacrylic acid-acrylamide (M2) (MA-AAm) and acrylic acid-acrylamide (M2) (AA-AAm) monomeric pairs. The copolymerization reactivity ratios deterined according to the Kelen-Tüdő method were: r1 = 1.35, r2 = 0.22 for the MA-AAm pair, and r1 = 1.75, r2 = 0.10 for the AA-AAm pair. It has been established that the polymerization rate depends both on the composition of the starting reaction mixture and on the reaction temperature. The differential kinetic curves obtained are unimodal ones, suggesting the occurrence of only one process, i.e. copolymerization. A second maximum in these curves, appearing at elevated temperature, is explained by crosslinking and formation of a water-insoluble fraction. The copolymers obtained are white powders; in contrast to their water-insoluble fractions, the water-soluble ones are not toxic but they are less active as immunomodulators.
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  • 26
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    Angewandte Makromolekulare Chemie 228 (1995), S. 201-219 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Hydrolyse von Poly(ester-urethan-harnstoffen) (PURUs) wurde untersucht. Es handelt sich dabei um einen komplexen Vorgang, der die Analyse der Beziehung zwischen der Zusammensetzung der PURUs und ihrer Hydrolysebeständigkeit erschwert. Es wurde gefunden, daß die Hydrolysebeständigkeit mit Zunahme (i) der Polyol-Acidität, (ii) des Estergruppen-Gehaltes, (iii) der Beweglichkeit der Hauptketten und (iv) deren Hydrophilie abnimmt; die Molmasse des Polyols scheint keinen merklichen Einfluß darauf zu haben. Der negative Einfluß von Ethergruppen (obwohl hydrolysebeständiger als Estergruppen) ist möglicherweise auf eine Zunahme der Hauptkettenbeweglichkeit und den dadurch leichteren Zugang von Wassermolekülen zu Estergruppen zurückzuführen. Der positive Effekt von aromatischen Ringen in Polyolen kann einer erhöhten Steifigkeit der Hauptkette als auch einer ansteigenden Hydrolysebeständig-keit benachbarter Estergruppen durch Resonanzeffekte zugeschrieben werden. Insgesamt kann angenommen werden, daß die beschriebenen Effekte sich überlagern und gleichzeitig die resultierende Hydrolysebeständigkeit vorherbestimmen. Es sollte daher möglich sein, qualitative Vorhersagen bezüglich der Hydrolysebeständigkeit in Abhängigkeit von der Zusammensetzung der PURUs zu treffen.
    Notes: Hydrolysis of poly(ester urethane ureas) (PURUs) is a complex phenomenon which impedes the analysis of the relationships between their composition and hydrolytic stability. Hydrolytic stability of PURUs decreases due to rising (i) polyol acidity, (ii) content of ester groups, (iii) flexibility and (iv) hydrophilicity of the backbones; molar mass of polyols does not seem to have any appreciable effect on it. Negative influence of ether groups (which have better hydrolytic stability than ester groups) is probably linked to the increase in the backbone flexibility and, consequently, to easier access of water molecules to ester groups. Positive effect of aromatic rings in polyols can be ascribed to enhanced rigidity of the backbones as well as to increased hydrolytic stability of adjacent ester groups due to the resonance effect. It can be presumed that the mentioned effects will superpose and simultaneously predestine the resulting hydrolytic resistance. Considering the observed tendencies, it is possible to qualitatively predict the trends how the hydrolytic stability will respond to changes in PURUs composition.
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  • 27
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    Angewandte Makromolekulare Chemie 229 (1995), S. 63-72 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine neuartige lichtempfindliche Naphthochinondiazid-Verbindung (NQD) wurde aus 2,6-Bis(hydroxymethyl)-3,4-dimethylphenol und Toluoldiisocyanat synthetisiert und mit IR-, NMR- und Elementaranalyse identifiziert. Die Bleicheigenschaften unter Lichteinwirkung wurden mit UV-Spektrophotometrie bestimmt. Die Anwendung von NQD in der Photolithographie als positiver Photoresist sowie einer wäßrigen Lösung von NQD, Novolak, Cellosolve-Acetat und DMF als lichtempfindliches Material wurde untersucht. Das hergestellte NQD erwies sich als effektive Komponente in positiven Photoresists. Die optimalen Bedingungen der UV-Dosis, Schichtdicke und Resistzusammensetzung wurden abgeschätzt. Die Auflösung des positiven Photoresists wurde durch Rasterelektronenmikroskopie bestimmt. Außerdem wurde der Einfluß von UV-Dosis und -Wellenlänge, Einwirkungsdauer und Entwicklungszeit auf die Empfindlichkeit und die Auflösung des Photoresists untersucht.
    Notes: A new photosensitive naphthoquinonediazide (NQD) was synthesized from 2,6-bis-(hydroxymethyl)-3,4-dimethylphenol and toluene diisocyante. NQD was identified by using IR, NMR and elemental analyses. Photobleachable characteristics were evaluated by UV spectrophotometry. Applications of the NQD on the photolithography as a positive working photoresist were investigated. The aqueous solution of NQD, novolak, cellosolve acetate, and DMF was used as a photosensitive material. It was found that NQD synthesized in this investigation can be used as an effective component in a positive photoresist. Optimal conditions of the UV dose, coating thickness, and development of the resist system were estimated. Resolution of the positive resist was evaluated by SEM technique. Effects of UV dose, exposure time, development time, and exposure UV wave length on the sensitivity and resolution of the photoresist were investigated.
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  • 28
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    Angewandte Makromolekulare Chemie 229 (1995), S. 123-132 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die radikalinduzierte Polymerisation von phenlysubstituierten 2-Methylen-1,3-dioxanen wurde untersucht. Es kann gezeigt werden, daß die grundlegende Polymerisationstendenz derartiger Ketenacetale darin besteht, über die Doppelbindung zu hochmolekularen Polyacetalen ohne eine nennenswerte Ringöffnung zu polymerisieren. Einflußfaktoren, wie z. B. resonanzstabilisierte Kettenenden oder sterische Hinderungen während des Wachstumsschrittes sind nicht in der Lage, die Polymerisation in die Richtung der gewünschten Ringöffnung zu lenken.Mittels Dichtemessungen wurden Informationen über das Schrumpfungsverhalten gewonnen. Es konnte gezeigt werden, daß raumerfüllende Substituenten am 2-Methylen-1,3-dioxansystem bei der Homopolymerisation grundsätzlich eine geringe Volumenschrumpfung bewirken und die Schrumpfung von herkömmlichen Monomeren bei der Copolymerisation herabsetzen können.
    Notes: We have investigated the free radical polymerization of phenyl-substituted 2-methylene-1,3-dioxanes. It was shown that there is a basic tendency of such ketenacetals to undergo exclusively a vinyl polymerization forming high-molecular polyacetals without any detectable ring opening. The polymerization with the desirable ring opening reaction cannot be controlled by factors like resonance stabilized chain ends or steric hindrance in the growing step.From densitometric measurements we got new information about the shrinkage behaviour. It was demonstrated that bulky substituents attached to the 2-methylene-1,3-dioxane system result in a significant low shrinkage in homopolymerization and the shrinkage of common comonomers can be decreased by copolymerization.
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  • 29
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    Angewandte Makromolekulare Chemie 229 (1995), S. 133-143 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Polymerisation von Acrylamid (AAM) in einer konzentrierten bikontinuierlichen Mikroemulsion wurde studiert. Die Initiierungsstelle bei Verwendung von radikalischen Initiatoren mit verschiedener Wasserlöslichkeit wurde untersucht. Es wurde festgestellt, daß ein vollständig oder teilweise wasserlöslicher radikalischer Initiator die Acrylamidpolymerisation in der untersuchten Mikroemulsion effektiv initiieren kann. Die dadurch entstandenen Polymeren weisen eine Spezialstruktur auf, die von der Zusammensetzung der ursprünglichen Mikroemulsion abhängig ist.
    Notes: The polymerization of acrylamide (AAM) in concentrated bicontinuous microemulsion systems was studied. The locus of initiation using radical initiators with various water-solubility was investigated. It was found that water-soluble and partially water-soluble initiators initiate the AAM polymerization in the reaction systems under investigation very effectively. The polymers thus formed have special structures dependent on the composition of the original concentrated bicontinuous microemulsion.
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  • 30
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    Angewandte Makromolekulare Chemie 229 (1995), S. 209-209 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 31
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    Angewandte Makromolekulare Chemie 229 (1995), S. 185-198 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bacteriorhodopsin is a component of the purple membrane of Halobacterium halobium. It shows photochemical activity and undergoes a series of photocyclic-associated conformational changes. Incorporated in a matrix it is suitable as a light energy/electrical current transducer. Very important is an orientation of purple membrane fragments.The reaction between solutions of a polyelectrolyte and multivalent ions leads to a ionotropic gel, that is a gel with an ordered structure. If the gel formation was carried out in the presence of purple membrane fragments, the Bacteriorhodopsin is highly oriented and produces a photoelectrical signal. It consists a correlation between the light direction and the orientation of the purple membrane due to the gel formation.
    Notes: Bacteriorhodopsin ist Bestandteil der sogenannten Purpurmembran des Mikroorganismus Halobacterium halobium. Es zeigt photochemische Aktivität und kann als biologischer Lichtwandler fungieren. Voraussetzung hierfür ist eine orientierte Anordnung der Purpurmembran in einer Matrix.Das Prinzip der ionotropen Gelbildung, d. h. die geordnete Strukturbildung einer Polyelektrolytlösung infolge eines gerichteten Diffusionsstromes von mehrwertigen Ionen gestattet die orientierte Anordnung der Purpurmembran. Durch Lichteinwirkung werden elektrische Signale induziert. Es besteht ein Zusammenhang zwischen der Richtung des Strahlungseinfalls und der durch die Gelwachstumsrichtung festgelegten Orientierung der Purpurmembran.
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    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal oxidation of β ray-crosslinked polyethylene (XLPE) was studied in temperatures ranging from 90 to 180°C. Various analytical methods were used for determination of an end of the induction period on bulk samples: gravimetry, ultimate tensile properties, density and color change. On microtome slices of ∼30 μm thickness the depth distribution of oxidation products, phenolic antioxidant, density and tensile ultimate properties were followed as a function of exposure time by respectively IR and UV spectrophotometry, densitometry and Microfoil Tensile Testing.Depending on the testing method different durations of induction period (DIP) were obtained. They increase in following order:Phenol depletion 〈 Ultimate elongation 〈 Density 〈 Carbonyl build-up ≤ Color change 〈 Weight loss.The difference between phenol depletion DIP and carbonyl build-up DIP can be considered as negligible at temperatures higher than the melting point (about 30%) but it reachs more than 100% at T〈 Tm.Different kinetic regimes of phenol consumption were observed depending on the exposure temperature. A mechanistic interpretation is proposed explaining the role of the stabilizer system in initially homogeneous and later heterogeneous oxidation of the bulk material.The Arrhenius law was applied to different durations of induction period. A discontinuity appeared in the melting point region (120-130°C) which is tentatively interpreted in terms of different stabilizer concentration in amorphous phase of semicrystalline material (T 〈 Tm) and in melt material (T 〉 Tm). On the basis of the presented complex study of polyethylene thermo-oxidation, different aspects of lifetime predictions are discussed.
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  • 33
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Most plastics are produced from oil and have a high potential as hydrocarbon sources for the chemical industry. Pyrolysis is a practicable way to pyrolyze mixed plastics. The fluidized bed pyrolysis has turned out to be particularly advantageous. 25 to 45 percent of product gas with a high heating value and 30 to 50 percent of an oil rich in aromatics, could be recovered. The oil is comparable to that of a mixture of light benzene and bituminous coal tar. Up to 60 percent of ethene and propene are produced by using mixed polyolefins as feedstock. Under appropriate conditions the pyrolysis could be successful on the market.
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  • 34
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: When poly(methyl methacrylate) films containing UV absorbers are exposed to UV light, the absorbers undergo photodegradation resulting in loss of absorbance. If the data extend for less than one half-life, both zero and first order kinetic treatment give fairly linear fits, but the rate constants so derived are dependent on the initial absorbance of the films. When the zero order rate constants are corrected to account for the higher rate of degradation near the surface compared with the bulk that occurs in highly absorbing films, consistent “infinite absorption” zero order rate constants are derived. The inhomogeneous degradation is due to only the highly absorbed, higher energy light contributing significantly to the degradation. For the benzophenone and benzotriazole classes of absorber, at least 65% of the degradation is due to light with wavelengths 〈 350 nm. Structural variations generally caused only small differences in the rates of degradation of these classes of absorbers unless the substitutions disrupted the intramolecular hydrogen bonds that are critical for stability. If the hydrogen bond is weakened, the absorber is less stable.
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  • 35
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aus Cardanol, einem Bestandteil der Schale der Cashewnuß, wurde durch Kondensation mit Formaldehyd und substituierten aromatischen Verbindungen unter saurer oder basischer Katalyse eine Reihe von Harzen hergestellt und anhand ihrer IR-Spektren charakterisiert. Sie lassen sich als selektive Ionenaustauscher für bestimmte Ionen verwenden, was mittels einer Gleichgewichtsmethode geprüft wurde. Das thermische Verhalten der Harze wurde untersucht, und ein plausibler Abbaumechanismus wird vorgeschlagen.
    Notes: A large number of resins have been synthesized by reacting cardanol, a constituent of cashewnut shell liquid, with formaldehyde and substituted aromatic compounds in the presence of acidic and basic catalysts. The resins have been characterized by IR spectra. They were shown to be selective ion exchangers for certain metal ions. A batch equilibrium method was used for studying the selectivity of the metal ions. The thermal behaviour of the resins has been studied and a plausible degradation mechanism has been suggested.
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  • 36
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Bisphenol A polycarbonate (BPA-PC) is an important high performance engineering thermoplastic well known for its outstanding combination of toughness, transparency and heat resistance. These properties make it an idel material for demanding applications where it is exposed to external stresses such as elevated temperatures, ultraviolet light and γ-ray sterilization. However, on extended exposure to these conditions, BPA-PC slowly degrades, turning progressively more yellow, eventually leading to a decrease in its physical properties. Over the years, there has been numerous studies made to understand these degradative processes so as to better design more stable BPA-PC formulations. In this paper, this chemistry is briefly reviewed along with more recent work in this area with a special emphasis on the efforts made to identifying the actual chemical species responsible for the observed yellow color and the chemistry responsible for their formation.
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  • 37
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hindered Amine Light Stabilizers (HALS) are know to inhibit the photo-oxidation of polymers. A key reaction in their stabilization mechanism is believed to be the conversion of a hindered aminoether into a nitroxyl radical. Several different possible mechanisms for this conversion were explored. One, the elimination of the aminoether to form an olefin and hydroxylamine (an intermediate in the formation of a nitroxyl), while possible at high temperatures, cannot account for the inhibitory activity we observed for secondary and primary aminoethers. Direct radical displacement by peroxy radicals was also considered. However, the products predicted by this reaction pathway were not observed. Finally, oxidation of the nitrogen by a peroxy radical, by either electron transfer or a radical attack on the nitrogen, was investigated. While electron transfer was shown to be unlikely, direct oxidation of the aminoether nitrogen was supported by our results. A detailed mechanism for the reaction of both alkyl- and acyl-peroxy radicals with aminoethers is proposed.
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  • 38
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die thermischen und dynamisch-mechanischen Eigenschaften einiger linearer kautschukelastischer Polyurethane mit chemisch unterschiedlichen starren Segmenten wurden untersucht und zur chemischen Zusammensetzung in Beziehung gesetzt. Interessante Zusammenhänge wurden zwischen der Kristallinität der elastischen Polyurethanharnstoffe und der aromatischen oder cycloaliphatischen Natur der Diisocyanat-Komponenten gefunden. Darüber hinaus scheinen die Ergebnisse bei einem bestimmten Verhältnis zwischen starren und flexiblen Segmenten und bei gegebener Zusammensetzung der flexiblen Gruppen auf eine bessere Phasenseparation bei den Polyurethanharnstoffen mit cycloaliphatischen starren Segmenten als bei solchen mit aromatischen, starren Einheiten hinzuweisen.
    Notes: Experimental batches of linear rubber-like polyurethanes characterized by the presence of chemically different hard segments are studied and their thermal and dynamic-mechanical properties are related to the differences in chemical compositions. Interesting correlations are found between the development of crystallinity in such elastomeric poly(urethaneurea)s and the aromatic or alicyclic nature of the diisocyanate. Moreover, for a fixed ratio between hard and soft segments, and for a given composition of the soft segment, the results seem to indicate a better degree of phase separation in cycloaliphatic-based hard segment poly(urethaneurea)s than in aromatic-based hard segment poly(urethaneurea)s.
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  • 39
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    Angewandte Makromolekulare Chemie 231 (1995), S. 135-144 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Makromonomere Polyethylenoxid-Azoinitiatoren (Makroinimere) MIM-400 und MIM-1500 wurden synthetisiert und IR- und NMR-spektroskopisch sowie mit Hilfe der DSC-Analyse charakterisiert. Die mit diesen Makroinimeren initiierte Dispersions-polymerisation von Styrol bzw. Methylmethacrylat (MMA) in Ethanol/Wasser bei 60°C wurde untersucht. Dabei wurde gefunden, daß die Polymerisationsgeschwindig-keit mit zunehmender MIM-Konzentration ansteigt, wobei der Anstieg im Styrolsystem ausgeprägter war. Im Bereich von mittleren Umsätzen konnte gezeigt werden, daß die Polymerisationsgeschwindigkeit von MMA proportional der Potenz 1,7 bzw. 1,6 von [MIM-400] bzw. [MIM-1500] ist, während für Styrol eine Potenz von 2,5 bezüglich [MIM-400] gefunden wurde.
    Notes: Macromonomeric poly(oxyethylene) azoinitiators (macroinimers) MIM-400 and MIM-1500 were synthesized and characterized by IR and NMR spectroscopy and DSC techniques. The dispersion polymerizations of styrene and methyl methacrylate (MMA) initiated by poly(oxyethylene) macroinimers (MIM-400 and MIM-1500) in water/ethanol were investigated at 60°C. The rate of polymerization was found to increase with increasing concentration of MIM and the increase was more pronounced in the styrene system. In the range of medium conversions the rate of polymerization was found to be proportional to the 1.7th and 1.6th power of [MIM-400] and [MIM-1500] for MMA and to the 2.5th power of [MIM-400] for styrene, respectively.
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  • 40
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    Angewandte Makromolekulare Chemie 231 (1995), S. 187-198 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Glass transition temperatures of binary and ternary blends of chemically uniform poly(styrene-co-n-butyl methacrylate)s with a mean content of 30.8 wt.-% of n-butyl methacrylate and number-average molar masses in the range of 4900 and 67000 g/mol have been investigated in relation to their composition. The blends showed significant deviations from an ideal behaviour with reference to a linearity between glass transition temperature and composition.This phenomenon is described by a mathematical model where polynoms are particularly well suited to represent the glass transition temperatures of the blends, partly exceeding those of the pure components. Finally, various reasons of these deviations were discussed. Here, energetical interactions seem to be of considerable importance combined with a nonadditivity of volumes.
    Notes: Die Glasübergangstemperaturen binärer und ternärer Mischungen chemisch einheitlicher Poly(styrol-co-n-butylmethacrylat)e mit einem mittleren n-Butylmethacrylat-Anteil von 30,8 Gew.-% und unterschiedlichen zahlenmittleren Molmassen im Bereich von 4900 bis 67000 g/mol wurden in Abhängigkeit von der Zusammensetzung untersucht. Es wurden wesentliche Abweichungen vom idealen Verhalten bezüglich einer linearen Abhängigkeit zwischen Glasübergangstemperatur und Zusammensetzung festgestellt.Dieses Verhalten konnte mit einem mathematischen Modell dargestellt werden, wobei sich insbesondere Polynome zur Beschreibung der teilweise über den Werten der Ausgangskomponenten liegenden Glasübergangstemperaturen der Mischungen als geeignet erwiesen. Schließlich wurden verschiedene Ursachen für diese Abweichungen diskutiert, wobei offensichtlich energetische Wechselwirkungen verbunden mit einer Nichtadditivität der Volumina von wesentlicher Bedeutung sind.
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  • 41
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    Angewandte Makromolekulare Chemie 233 (1995), S. 133-148 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: ε-Caprolactam (CL) and phenyl glycidyl ether (PGE) were homopolymerized using the initiator/accelerator-systems Na-caprolactam/N-acetyl-caprolactam (NaCL/AcCL) and Na-caprolactam/N-acetyl imidazole (NaCL/AcImi). In a one-pot reaction both monomers gave different oligomeric reaction products depending on the reaction temperature (100°C to 140°C, max. 240°C) but no regular copolymers. Soluble products were separated by HPLC and identified by means of spectroscopic methods. In acetone insoluble products were investigated by IR- and NMR-spectroscopy, mass spectrometry and elemental analysis.
    Notes: Es wurden Versuche zur Homopolymerisation von ε-Caprolactam (CL) und Phenylglycidether (PGE) mit den Initiator/Beschleuniger-Systemen Na-Caprolactam/N-Acetylcaprolactam (NaCL/AcCL) und Na-Caprolactam/N-Acetylimidazol (NaCL/AcImi) durchgeführt, um die für eine mögliche Copolymerisation von CL und PGE geeigneten Reaktionsbedingungen zu ermitteln. CL und PGE wurden in unterschiedlichen molaren Verhältnissen (CL : PGE = 1 : 5 bis 1 : 0,05) und bei Temperaturen zwischen 100°C und 140°C (max. 240°C) in einer Eintopfreaktion polymerisiert.Die löslichen Produkte wurden mittels HPLC getrennt und spektroskopisch identifiziert. Die in Aceton unlöslichen Produkte wurden mit IR- und NMR-Spektroskopie, Massenspektrometrie (MS) und Elementaranalyse untersucht.
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  • 42
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    Angewandte Makromolekulare Chemie 236 (1996), S. 111-127 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Neuartige Fluoropolyether-Polyol-Harze, die mit konventionellen Härtern wie Polyisocyanaten oder Melaminen aushärtbar sind, wurden hergestellt. Zunächst wurden oligomere NCO-terminierte Prepolymere durch Addition von Fluorpolyether-Makrodiolen unterschiedlicher Molekulargewichte an Isophorondiisocyanate erhalten. Durch die Reaktion dieser Prepolymeren mit Trimethylolpropan wurden endständige Hydroxygruppen eingeführt. Die Viskosität von Lösungen dieser Harze wurde bei unterschiedlichen Konzentrationen (Massenbruch 0,4-0,8) und Temperaturen (25°C-65°C) gemessen. Die erhaltenen Werte wurden auf der Basis der Erickson-Gleichung (Konzentrationsabhängigkeit von η) und unter Berücksichtigung des WLF-und des Arrhenius-Modells (Temperaturabhängigkeit von η) diskutiert. Das thermische Verhalten der Harze und von ausgehärteten Filmen wurde mit DSC bestimmt. Dabei wurden zwei Glasübergange beobachtet, die den separierten fluorhaltigen und nicht-fluorhaltigen Phasen zugeordnet werden können. Die Analyse des Zugverhaltens der Filme zeigte besonders bei den mit Isocyanat gehärteten Proben ein ausgeprägtes hart-plastisches Verhalten. Diese Werkstoffe erscheinen für die Anwendung als hoch-wertige, dauerfeste und klare Beschichtungen geeignet.
    Notes: New fluoropolyether polyolic resins are presented suitable to be cured with conventional hardeners as polyisocyanates or melamines. These resins are prepared by addition of fluoropolyether macrodiols (Fomblin® ZDOLTX) of various molecular weights to isophorone diisocyanate (IPDI) to give oligomeric NCO-terminated prepolymers. The final hydroxy functionality is obtained by the reaction of those prepolymers with trimethylolpropane (TMP). The viscosity of the resins is measured at various concentrations (weight fraction 0.8 - 0.4) and temperatures (T = 25-65°C). The results are discussed in terms of the Erickson equation (η vs. concentration) and using the WLF and Arrhenius models (η vs. T). The thermal behavior is studied by DSC for both the resins and cured films indicating the presence of two Tgs, corresponding to the segregated fluorinated and hydrogenated phases, the former particularly evident with the highest molecular weights of the fluorinated macromer. Tensile curves of selfsupported films are then analyzed showing an evident tough-plastic behavior especially for the isocyanate-cured films. The application of such materials as high-durability clear coats is finally proposed.
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  • 43
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    Angewandte Makromolekulare Chemie 237 (1996), S. 1-44 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zur Verbesserung der Maßhaltigkeit und der Zähigkeit von gehärteten Melamin-Formaldehyd-Harz-Formmassen (MF) wurden teilverträgliche, methylolgruppenhaltige Epoxidharze (EP) auf Bisphenol A-Basis hergestellt und charakterisiert. Die Vernetzung solcher Epoxyresolharze durch 2-Ethyl-4-methylimidazol in Gegenwart von MF-Harz wurde untersucht. Spritzgepreßte Probekörper zeigen eine Zweiphasenstruktur; die EP-Phase kann als Wirt für carboxy-funktionalisierte, oligomere NBR-Kautschuke (CTBNX) dienen, die für sich allein in MF-Harzen nicht wirksam sind. Unter der Voraussetzung von kovalenten Bindungen in der Phasengrenzfläche kann durch den Zusatz von 0,5 bis 4 Gew.-% CTBNX zur MF-Formmasse bei EP-Anteilen bis 20 Gew.-% eine 50 bis 100proz. Steigerung von Bruchdehnung und Schlagzähigkeit erreicht werden, ohne daß Steifigkeit und Wärmeformbeständigkeit wesentlich abfallen. Bei moderaten EP/CTBNX-Gehalten wird zusätzlich die Nachschwindung von MF-Formteilen vermindert.
    Notes: In order to improve dimension stability and toughness of melamine formaldehyde moulding materials (MF), compatible bisphenol A epoxy resins (EP) with additional methylol groups were synthesized and characterized. Crosslinking of those epoxyresol resins with 2-ethyl-4-methylimidazole in the presence of MF resin was investigated. Transfer-moulded specimens revealed a two-phase morphology in which the EP phase is used as a host for modification with carboxylic functionalized oligomeric NBR rubber (CTBNX), which is not effective in MF moulding materials alone. The addition of 0.5 - 4 wt.-% CTBNX to the MF moulding materials at an epoxy content of maximum 20 wt.-% results in 50-100 % increase of elasticity and toughness without serious decrease in stiffness and heat deflection temperature, provided that covalent interfacial bonds exist. In addition, the post-shrinkage of MF parts decreases if a moderate EP/CTBNX content is introduced.
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  • 44
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    Angewandte Makromolekulare Chemie 238 (1996), S. 11-30 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der gleichzeitige Einfluß des Verhältnisses von Fließhilfsmittel (Paraloid K 120N), Rußart und Schlagzähmodifikator (CPE 3615 und Kane Ace B56 A) auf die wichtigsten physiko-mechanischen Eigenschaften unplastifizierter PVC-Mischungen wurde studiert.Die erhaltenen Resultate wurden mathematisch verarbeitet und graphisch als Funktionsflächen dargestellt. Bemerkenswert ist, daß die Einführung von 2,5 und 5 Teilen Ruß eine Verbesserung der physico-mechanischen Eigenschaften ermöglicht. Dieses Resultat ist durch die Anwesenheit der Schlagzäh- und Fließmodifikatoren zu erklären.
    Notes: The concurrent influence of the processing aid (Paraloid K 120N) and the carbon black ratio, as well as the nature and the ratio of the impact modifier (CPE 3615 and Kane Ace B56 A) on the main physico-mechanical characteristics of the poly(vinyl chloride)-based unplasticized mixtures have been studied. The results obtained, processed mathematically and plotted graphically in the form of response surfaces, evidenced that the improvement of certain physico-mechanical properties becomes possible by the introduction of 2.5 parts and 5.0 parts carbon black into these compounds. This is due to the introduction of impact modifiers and processing aids into the mixtures.
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  • 45
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    Angewandte Makromolekulare Chemie 238 (1996), S. 63-71 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Reihe neuartiger Polyhydrazide mit endständigen Phenoxygruppen wurde aus äquimolaren Anteilen von Dicarbonsäuredichloriden und Phenoxyterephthalsäuredihydrazid durch Lösungspolykondensation in N-Methyl-2-pyrrolidinon (NMP) bei niedriger Temperatur hergestellt. Durch thermische Cyclisierung der Polyhydrazide wurden die entsprehchenden Poly(1,3,4-oxadiazol)e mit endständigen Phenoxygruppen erhalten. Die Polymeren wurden durch Viskosimetrie, Löslichkeitsuntersuchungen, IR-Spektroskopie, Differentialkalorimetrie und Thermogravimetrie charakterisiert.
    Notes: A series of new polyhydrazides containing pendent phenoxy groups has been synthesized by low-temperature solution polycondensation of equimolar amounts of diacid dichlorides and 2-phenoxyterephthalic dihydrazide in N-methyl-2-pyrrolidi-none (NMP). The thermal cyclization of the polyhydrazides gave the corresponding poly(1,3,4-oxadiazole)s containing pendent phenoxy groups. The polymers were characterized by viscometry, solubility measurements, IR spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis.
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  • 46
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    Angewandte Makromolekulare Chemie 238 (1996), S. 105-117 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein Ethylen-Vinylacetat-Copolymeres (EVA) mit 12% Vinylacetat-Gehalt wurde mit Trimethylolpropantrimethacrylat (TMPTMA) als Sensibilisator mit Elektronen bestrahlt. Die mechanischen und elektrischen Eigenschaften der bestrahlten Copolymerproben wurden untersucht. Die Resultate zeigen, daß sich Zugfestigkeit und Bruchdehnung zunächst mit zunehmender Strahlungsdosis verbessern und bei Überschreiten einer optimalen Strahlungsdosis und Sensibilisatorkonzentration wieder verschlechtern. Durch die Bestrahlung wird eine Vernetzung des Polymeren ausgelöst, die auf den sich mit der Strahlungsdosis erhöhenden Gelanteil zurückgeführt wird. Im Vergleich mit den Originalproben nehmen sowohl die Dielektrizitätskonstante als auch der dielektrische Verlustfaktor durch die Elektronenbestrahlung ab.
    Notes: Ethylene-vinyl acetate (EVA) copolymer (12% vinyl acetate content) is subjected to electron beam irradiation using trimethylolpropane trimethacrylate (TMPTMA) as a radiation sensitizer. Mechanical and electrical studies of these irradiated samples show that the strength properties (tensile strength, elongation at break) are increased with radiation dosage up to an optimum radiation dose and sensitizer level above which the properties begin to deteriorate. Crosslinking of the polymer takes place on irradiation which is attributed to an increased gel content with increasing radiation dose. Compared to the original samples both dielectric constant and dielectric loss factor decrease for samples subjected to irradiation.
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  • 47
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    Angewandte Makromolekulare Chemie 238 (1996), S. 143-163 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Cellulose-p-toluolsulfonsäureester (Cellulosetosylate) lassen sich durch homogene Umsetzung von Cellulose in einer Lösung aus N,N-Dimethylacetamid und LiCl mit Tosylchlorid (Tos-Cl) und Triethylamin in 24 h bei 8°C in hoher Ausbeute und mit minimalem Einbau von Chlordesoxy-Gruppen herstellen. Die unterschiedlichen Celluloseausgangsmaterialien hatten durchschnittliche Polymerisationsgrade von 280 bis 5100. Die Produkte wurden mit Elementaranalyse, 13C-NMR- und FTIR-Spektroskopie und durch Bestimmung der Grenzviskositäten charakterisiert. Die Erhöhung des Molverhältnisses Tos-Cl/Anhydroglucose-Einheit (AGU) von 0.6 auf 9.0 führte zu einem Anstieg des Substitutionsgrades (DS) von 0.4 bis auf einen Maximalwert von 2.3. Die Cellulosetosylate sind in herkömmlichen organischen Lösungsmitteln wie Dimethylsulfoxid (im gesamten DS Bereich) und in N,N-Dimethylacetamid, N,N-Dimethylformamid, Aceton, Tetrahydrofuran und Trichlormethan (in Abhängigkeit von DS) löslich. Durch 13C-NMR-Spektroskopie wurde nachgewiesen, daß die Tosylierung am O-6 Atom der AGU schneller als an den O-2/3 Atomen erfolgt. Die Analyse der korrespondierenden Ioddesoxycellulosen, die durch Umsetzung mit NaI in Acetylaceton synthetisiert wurden, bestätigte dies zusätzlich. Darüber hinaus wurden wichtige Eigenschaften der Cellulosetosylate wie die Stabilität gegenüber Alkali und thermischer Beanspruchung untersucht.
    Notes: Pure cellulose p-toluenesulfonates (tosylates) with an insignificant formation of chlorodeoxy groups were prepared by reacting cellulose dissolved in a solution of N,N-dimethylacetamide and LiCI with tosylchloride (Tos-CI) in the presence of triethylamine within 24 h at 8°C. Various cellulosic starting materials with a degree of polymerization from 280 to 5 100 were used. The samples obtained were characterized by means of elemental analysis, FTIR and 13C NMR spectroscopy, and their intrinsic viscosities. The rise of the molar ratio of Tos-CI/anhydroglucose unit (AGU) from 0.6 to 9.0 leads to an increase in the degree of substitution (DS) from 0.4 up to a maximum value of 2.3. The cellulose tosylates are readily soluble in common organic solvents like dimethyl sulfoxide (within the whole DS range) and in N,N-dimethylacetamide, N,N-dimethylformamide, acetone, tetrahydrofuran and trichloromethane depending on DS. As revealed by 13C NMR spectroscopy a faster tosylation takes place at the O-6 atom of AGU compared with the O-2/3 atoms. This was additionally confirmed by analysis of the corresponding iododeoxy celluloses synthesized with NaI in acetylacetone. Furthermore, some important properties as stability against alkaline and heat were studied as well.
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  • 48
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    Angewandte Makromolekulare Chemie 239 (1996), S. 27-32 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Herstellung einer SiC-Oberfläche auf Kohlefasern unter Verwendung einer Sol-Gel-Mischung von Tetraethylorthosilikat (TEOS) und Phenolharz wurde untersucht. FTIR- und SEM-Untersuchungen zeigten, daß die SiC-Oberfläche durch carbothermische Reduktion der Sol-Gel-Mischung bei 1 420°C innerhalb von 15-20 min in einer Argon-Atmosphäre gebildet werden kann. Mittels TGA konnte gezeigt werden, daß die SiC-Beschichtung die thermo-oxidative Stabilität der Kohlefasern erhöht. Bei der erreichten SiC-Schichtdicke von 0,47 μm, bei einem C/Si-Verhältnis von 4, zeigt sich keine Beeinflussung der mechanischen Stabilität der Kohlefasern.
    Notes: The preparation of a SiC coating on a carbon fiber surface using a sol-gel mixture of tetraethyl orthosilicat (TEOS) and phenolic resin was studied. FTIR and SEM investigations indicated that the SiC coating can be formed by carbothermal reduction of the sol-gel mixture at 1420°C for 15-20 min in an argon atmosphere. TGA of the coated fiber was also performed, showing that the SiC coating improves the thermooxidative stability of the carbon fiber. With the thickness of the obtained coating of 0.47 μm using a C/Si ratio of 4, this treatment does not affect the carbon fiber strength.
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  • 49
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    Angewandte Makromolekulare Chemie 239 (1996), S. 55-62 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Diese Mitteilung behandelt den Einfluß von oligomeren Polypropylen- und Polybutylenölen mit unterschiedlichem Molekulargewicht auf die adhäsiven Eigenschaften von ataktischem Polypropylen (aPP) und dessen Mischungen mit einem Styrol-Ethylhexylacrylat-Copolymeren. Die mechanische Adhäsionsarbeit Am von Mischungen, die ataktisches Polypropylen und das Oligomere enthalten, steigt mit dem Molekulargewicht des Oligomeren, was im Fall des Propylenöls signifikanter ist. Im Fall der ternären Mischungen des ataktischen Polypropylens mit dem Styrol-Ethylhexylacrylat-Copolymeren und Oligomeren wird ein Adhäsions-Maximum beobachtet, wenn der Gehalt an Styrol-Ethylhexylacrylat-Copolymeren in der Mischung ungefähr 30 Gew.-% erreicht. Wenn kein Oligomeres in der Mischung vorhanden ist, kann man bei dieser Zusammensetzung ein Adhäsions-Minimum beobachten, was auf die Unverträglichkeit der übrigen Komponenten zurückzuführen ist.
    Notes: This paper deals with the influence of oligomers, namely propylene oil and butylene oil, of different molecular weight on the adhesive properties of atactic polypropylene (aPP) and its mixtures with styrene-2-ethylhexyl acrylate (S-EHA) copolymer. The mechanical work of adhesion Am of the mixture containing atactic polypropylene and oligomer increases with the molecular weight of the oligomer, which was more significant in the case of propylene oil. For ternary mixtures aPP-S-EHA copolymer/oligomer a maximum of adhesion can be observed if the content of the S-EHA copolymer in the mixture reaches about 30 mass-%. In the absence of oligomers in the mixture a minimum of adhesion can be observed for this composition, which can be attributed to the incompatibility of the remaining components.
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  • 50
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: After comparison of three catalyst systems, i.e. [Nd(Oct)3/Al2Cl3ET3/Al(i-But)3, Ni(Oct)2/BF3OEt2/AlEt3 and Al(i-But)3/I2/TiCl4] the titanium catalyst system was used for the copolymerization of 1,3-butadiene with propylene oxide. The effects of monomer ratio on copolymer composition, conversion, microstructure, molar mass and molar mass distribution as well as of time of polymerization and of the aluminium/titanium ratio were evaluted. The copolymerization parameters were determined according to Kelen-Tüdős as rbutadiene = 0,9 and rpropylene oxide = 3,9. Copolymerization was confirmed by 13C NMR spectroscopy and extract evaluation combined with 1H NMR spectroscopy.
    Notes: Für die Copolymerisation von 1,3-Butadien mit Propylenoxid wurde nach dem Vergleich der drei Katalysatorsysteme Nd(Oct)3/Al2Cl3ET3/Al(i-But)3, Ni(Oct)2/ BF3OEt2/AlEt3 und Al(i-But)3/I2/TiCl4 das Titankatalysatorsystem eingesetzt. Neben dem Einfluß der Monomerzusammensetzung auf den Umsatz, die Microstruktur, die Copolymerzusammensetzung, die Molmassen sowie die Molmassenverteilungen wurden auch die Polymerisationszeit und das Aluminium/Titan-Verhältnis untersucht. Die Copolymerisationsparameter wurden nach Kelen-Tüdős zu rButadien = 0,9 und rPropylenoxid = 3,9 bestimmt. Der Copolymernachweis erfolgte über 13C-NMR-Spektroskopie und Extraktionsuntersuchungen in Verbindung mit 1H-NMR-Spektroskopie.
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  • 51
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    Angewandte Makromolekulare Chemie 239 (1996), S. 191-199 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Phosphorhaltige Polyurethane (PU-P) auf der Basis von Bisphenol A wurden durch N-Alkylierung hergestellt und mittels IR- und 1H NMR-Spektroskopie charakterisiert. Physikalische und thermische Eigenschaften dieser Polyurethane wurden mittels Differentialkalorimetrie, Thermogravimetrie, Röntgenbeugung und Untersuchungen der Löslichkeit, der Feuerbeständigkeit (Sauerstoffindex, LOI) und der reduzierten Viskosität bestimmt. Die Glastemperaturen der N-alkylierten Polymeren sanken von 120°C für das Ausgangspolymere bis auf 29°C für das N-alkylierte Polyurethan mit 2 Gew.-% Phosphor. Die Viskosität der N-alkylierten Polyurethane nahm von 0,36 dL g-1 auf 0,24 dL g-1 ab. Die phosphorhaltigen Polyurethane besitzen eine geringere thermische Stabilität und bessere Löslichkeit sowie höhere Feuerbeständlgkeit als das Ausgangspolymere. Die Röntgenstreuexperimente ergaben, daß ein erhöhter Phosphorgehalt der Polyurethane die Kristallinität herabsetzt.
    Notes: Phosporus-containing polyurethanes (PU-P) based on bisphenol A were prepared by N-alkylation. The structures of N-alkylated polyurethanes were characterized by IR and 1H NMR spectra. Physical and thermal properties of the phosphorus-containing polyurethanes were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction, tests of solubility, limiting oxygen index (LOI) and reduced viscosity. Tg of the N-alkylated polymers decreased from 120°C for the starting polymer to 29°C of the 2.0 wt.-% phosphorus-containing polyurethanes. The viscosity of N-alkylated polyurethanes also decreased from 0.36 dL g-1 to 0.24 dL g-1. The thermal stability of polyurethanes decreased on the introduction of phosphorus groups. The LOI values of polyurethanes showed that fire resistance of phosphorus-containing polyurethanes was enhanced. X-ray diffraction measurements showed that the increased phosphorus content was accompanied by decreased crystallinity of the polyurethanes. The solubility of PU-P was improved.
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  • 52
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This question was addressed using various methods to monitor the process of curing and state of the final network. Attention was particularly focused on the possible inhomogeneous network formation as a consequence of the crosslinking process. An analysis of experimental data has revealed that some cured resins can be considered as homogeneous as the corresponding uncrosslinked materials. Resins cured by simple stepwise alternating chemistries, with good compatibility of components, usually fulfill the criterion of homogeneity. A family of epoxy resins cured with polyamines belongs to this category. Nodular structures seen by electron microscopy are a result of interaction of the electron beam or etching. Such structures are also observed for uncrosslinked polymers investigated under the same conditions. Formation of inhomogeneities in a number of thermoset systems is due to (a) chainwise mechanism of network formation with fast propagation inducing cyclization and steric volume exclusion and (b) poor compatibility of components of the system made stronger by increasing molecular weights and crosslinking during curing. Networks formed by freeradical polymerization and copolymerization of polyvinyl monomers can serve as an example of crosslinking-driven formation of inhomogeneities.
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  • 53
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The base and transition metal catalyzed isomerization of allyl and crotyl ethers affords a facile, high yield route to the preparation of a variety of mono-, di-, and multifunctional 1-propenyl and 1-butenyl ethers. Employing this novel method, monomers containing epoxide, ester, ether carbonate and urethane groups can be prepared from their readily available allyl and crotyl precursors. In general, these monomers display very high reactivity in cationic polymerizations. In our work, we have focused on photoinduced cationic polymerizations of these monomers using diaryliodonium and triarylsulfonium salt photoinitiators. To study these very fast photopolymerizations, extensive use of real-time infrared spectroscopy was made. Employing this technique, the effects of monomer and photoinitiator structure on the rates of polymerization were studied.
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  • 54
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    Angewandte Makromolekulare Chemie 240 (1996), S. 137-149 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rubber elasticity is associated with changes in configurational entropy of a long chain. Because the chain cannot change its configuration instantaneously, there is a time delay in deformation to an applied force. This delayed response is the source of viscoelasticity and hysteresis energy loss of elastomer networks. Many tire performance properties are related to the viscoelasticity of tire components. Wet and dry traction of tire is related to the energy loss of the tread material at very high frequencies. On the other hand, rolling resistance of tire is characterized by the energy loss of tread material at relatively low frequencies. The dynamic viscoelastic properties of elastomer network shows characteristic zones on a frequency scale. At very high frequencies the energy loss is controlled by the segmental motions of the polymer chain. At lower frequencies the energy loss is related to the longer range motions of the chain. A series of polymers was synthesized to study the effect of micro- and macro-structure of the polymer on the viscoelastic properties of tread compounds and their tire performance properties. As expected from the theory, the wet traction of the tire was highly correlated to the segmental motions of the chains; namely, the glass transition temperature of the polymer. The energy loss of the compounds at a higher temperature, however, was related to the macrostructure of the polymer chain. Those examples illustrate that the fundamental understanding of the theory of elastomer network allows a tire engineer to obtain the best balance of tire performance characteristics.
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  • 55
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    Angewandte Makromolekulare Chemie 240 (1996), S. 171-180 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cationic, anionic, and radical ring-opening polymerization of spiro and bicyclic monomers, and their application to network polymers have been developed. Bicyclo orthoesters (BOEs), spiro orthoesters (SOEs), and spiro orthocarbonates (SOCs) were polymerized by cationic double ring-opening. Bicyclobis(γ-butyrolactone)s and spirobis(γ-butyrolactone)s were copolymerized with epoxides by anionic alternating ring-opening. Polymers from SOCs bearing exomethylene groups consisted of ring-opened and vinyl polymerized units. The degree of ring-opening of SOCs depended upon the number of rings and steric hindrance. The radical polymerization of vinylcyclopropanone cyclic acetals depended on the ring-size. With the monomers bearing 5- and 6-membered acetal rings, single ring-opened polymers were obtained. With the monomer bearing 7-membered acetal ring, the polymer mainly consisted of double ring-opened unit. These monomers could be crosslinked by bifunctionalization. Poly(cyclic orthoester)s linked by covalent bonds with dithiols to bifunctional SOEs were crosslinked by acid catalysts, and the reversible crosslinking-depolymerization system could be controlled by temperature.
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  • 56
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    Angewandte Makromolekulare Chemie 240 (1996), S. 205-211 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyester urethane network elastomers with incorporated hard segment oligomers have been prepared by poly(ethylene adipate)glycol (PEA), 2,4-tolylene diisocyanate (TDI), and 1,4-butanediol (BD). These hard segment oligomers were hydroxy-terminated oligomers ([BD-TDI]n-BD; n=1,3), obtained by reacting BD with TDI. Concentrations of allophanate as a cross-linking site were determined by the amine degradation method. Hard segment moieties were obtained by a novel selective hydrolysis of soft segments in the elastomers. Molecular weight distributions of hard segment were measured by means of GPC. Mechanical and thermal properties were measured. Dependence of rubber elasticity on physical cross-linking between normal elastomers and the elastomers with incorporated hard segment oligomers were discussed.
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  • 57
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly (vinyl alcohol) with pendent styrylpyridinium groups (SbQ) is insolubilized by photoirradiation. An association takes place in SbQ groups. The association of polymer chains becomes marked with increasing the number of SbQ groups. Mainly intermolecular crosslinks were formed. Transparent and homogeneous macrogels consisting of several intermolecular crosslinks are obtained.The proportion of the free water to the bound water in PVA-SbQ gels was 3.3-2.9 despite of the large change in conversion of photodimerization of SbQ groups, x=0.27-0.58. The water uptake after swelling of the gels in water increased 6-27 times compared to the original weight at pH=7. The higher the degree of photocrosslinking, the lower was the degree of swelling. The water diffusion coefficients, D, were (2.2-5.8) × 10-5 cm2 S-1 for a 88% saponified PVA with 1 . 3 mol% SbQ groups. The volume of the gel increased discontinuously about 10-fold for the 99% saponified PVA with 0 . 096 mol% SbQ and 51% water (49% acetone). The acetone concentration at the transition decreased with increasing the degree of saponification of the PVA.
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  • 58
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    Angewandte Makromolekulare Chemie 239 (1996), S. 151-160 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch anionische Copolymerisation von Allylmethacrylat und Methylmethacrylat wurden Makromonomere unterschiedlicher Kettenlänge mit durchschnittlich drei Allyl-Doppelbindungen pro Kette hergestellt́ und mit NMR-Spektroskopie und Gelpermeationschromatographie charakterisiert. Durch Copolymerisation der Makromonomeren mit 1-Vinyl-2-pyrrolidon wurden dreidimensionale Strukturen erhalten. Die optischen und mechanischen Eigenschaften der Produkte wurden untersucht, und die Quellungseigenschaften und Vernetzungsgrade wurden bestimmt. Die Copolymereigenschaften wurden durch Makromonomere mit Kettenlängen bis 40 Einheiten nur wenig beeinflußt. Bei Kettenlängen über 50 Einheiten wurde eine leichte Abnahme der Wasseraufnahmefähigkeit und eine deutliche Erhähung des Elastizitätsmoduls beobachtet. Die Vernetzungsgrade hängen von der Makromonomer-Kettenlange ab; eine merkliche Erhöhung aufgrund der groößeren Zahl an Methyl-Methyl-Wechselwirkungen wurde bei Kettenlangen über 50 Einheiten festgestellt. Die Copolymeren zeigen günstige Festigkeits-Dehnungs-Eigenschaften und einen geringen Gehalt an wasserlöslichen Extrakten, in denen durch IR-Spektroskopie 1-Vinyl-2-pyrrolidon-Homopolymere identifiziert wurden. Obwohl mit allen untersuchten Makromonomeren gute Resultate erzielt wurden, scheint für die Copolymerisation mit 1-Vinyl-2-pyrrolidon das Makromonomere mit 50 Einheiten am besten geeignet.
    Notes: Macromonomers of various chain lengths with an average of three allyl double bonds per chain were prepared by anionic copolymerization of allyl methacrylate with methyl methacrylate. The macromonomers were characterized by gel permeation chromatography and nuclear magnetic resonance. The macromonomers were then copolymerized with 1-vinyl-2-pyrrolidone to form three-dimensional structures. Their optical, swelling and mechanical properties were studied and the crosslinking efficiency was determined. The copolymer properties are not greatly affected by macromonomer chain lengths up to 40-mers; above 50-mers there is a slight decrease in the equilibrium water content and a significant increase in the modulus of elasticity. The crosslinking efficiency depends on the macromonomer chain length; a marked increase was observed for the 50-mer because of a greater number of methyl-methyl interactions. Copolymers have favourable strength-strain properties and a low content of water-soluble extracts, in which the IR analysis demonstrated the presence of 1-vinyl-2-pyrrolidone homopolymers. In spite of the good results obtained for all the macromonomers described in this work, the 50-mer seems to be optimal for copolymerization with 1-vinyl-2-pyrrolidone.
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  • 59
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    Angewandte Makromolekulare Chemie 239 (1996), S. 201-213 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The curing of diglycidyl ether of bisphenol A (DGEBA) with 2,6-dimethylol-p-cresol modified by hexahydrophthalic acid anhydride was investigated and compared with the analogous in situ curing of DGEBA, hexahydrophthalic acid anhydride and 2,6-dimethylol-p-cresol. The chemical reactions were investigated by means of titration and different spectroscopic and chromatographic methods. It was examined whether the less complicated and therefore cheaper in situ reaction delivers postcured products with equal or better properties. Furthermore, it was investigated whether the results are similar using technical phenolic hardeners.
    Notes: Die Härtung von Diandiglycidylether (DDGE) mit hexahydrophthalsäureanhydridmodifiziertem 2,6-Dimethylol-p-kresol (HHPSA-DMPK) wurde untersucht und mit der in situ durchgeführten Vernetzung von DDGE mit Hexahydrophthalsäureanhydrid (HHPSA) und 2,6-Dimethylol-p-kresol (DMPK) verglichen. Die chemischen Reaktionen wurden durch Titration der Epoxidgruppen und mit verschiedenen spektroskopischen und chromatographischen Methoden untersucht. Es wurde geprüft, ob die weniger aufwendige und daher preiswertere in situ-Härtung zu Produkten mit gleichen oder besseren Endeigenschaften führt. Weiterhin wurde die Übertragbarkeit der Ergebnisse auf den Einsatz technischer Phenolharzhärter getestet.
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  • 60
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zur Entwicklung neuartiger ökologisch verträglicher makromolekularer Schlichtemittel wurden in früheren Arbeiten Copolymerisationsreaktionen zwischen Polyvinylalkohol (PVA) und Stärke unter Verwendung von chemisch reaktiven bifunktionellen Verbindungen wie N-Methylolacrylamid beschrieben. Im Rahmen dieser Arbeit werden die physikochemischen Eigenschaften des resultierenden Copolymeren untersucht. Von Bedeutung sind hierbei insbesondere Merkmale wie Molekulargewichtsverteilung, Klebekraft, Stabilität, Löslichkeit sowie rheologische Eigenschaften. Derartige Kenntnisse über die physikochemische Beschaffenheit der PVA-Ausgangsverbindung sowie des makromolekularen Endproduktes sind eine wesentliche Voraussetzung für die Entwicklung von neuen Produkten, die als wasserlösliche, recycelbare Schlichtemittel zur Anwendung in der Textilindustrie kommen können.
    Notes: A macromolecular sizing agent based on the copolymerization of poly(vinyl alcohol) (PVA) with hydrolysed starch was prepared using the chemically reactive bifunctional compound N-methylolacrylamide. Detailed characteristics of the resultant PVA/N-methylolcarbamoylethylated starch copolymer were studied where emphasis has been placed on solubility, rheological properties, molecular weight distribution, adhesive power and stability. Elucidation of the nature of the macromolecular segments of both N-methylolcarbamoylethylated PVA as well as PVA/N-methylolcarbamoylethylated starch copolymer fulfilled the prerequisite to tailor PVA/starch copolymer which is appropriate for application as a water-soluble recyclable sizing agent by ultrafiltration.
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  • 61
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Seismic isolation was reconfirmed to be extremely efficient for the protection of buildings, and hence human life, on the occasion of the Great Hanshin Earthquake. Rubber bearings are placed under the buildings for isolation, and thus the type of rubber bearings is a dominant factor for efficient isolation. In this report, the performance of peripherally restraining type rubber bearing (PRB) was examined where its contracted model was found to simulate the performance of full scale PRB precisely. Damping ratio and vertical spring constant of PRB are as good as the existing ones. PRB showed lower critical shear strain, but it was concluded that no problems were found for the actual use of PRB.
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  • 62
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The network formation of phenol-formaldehyde resin was investigated by the Monte Carlo (MC) simulation technique. The observed value of the gel point, pc, was exactly determined as a critical extent of reaction, where the Mw/Mn in soluble parts is maximum. The MC simulation with the cubic percolation theory was applied to the gelation of phenolic resins and gave an exact gel point, which was in excellent agreement with the observed value of pc. The simulation showed that the intramolecular reaction occurred frequently with increasing the gel fraction beyond the gel point. The structural analysis of the maximum cluster with the computer strongly supported the contribution of the intramolecular reaction to the network formation of the gel.
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  • 63
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structure of the hydrogel of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) was investigated by small angle X-ray scattering (SAXS) of synchrotron radiation. A physically crosslinked blend gel, which was prepared by repetitive freezing and thawing of an aqueous solution of PVA and PAA, could be chemically crosslinked by esterfication of PVA with PAA even in the hydrogel state. The chemical crosslinking induced the destruction of physical crosslinks into a folded structure, indicating that the chemical crosslinking proceeds at the sites around the physical crosslinks that contain PVA and PAA in much higher concentration than other portion of the gel. The pH-induced structure changes of the PVA hydrogels, chemically crosslinked with poly(acrylic acid) (PAA) were investigated by SAXS on the samples of various chemical crosslinking time. The gels were shrunk at pH4, and swollen at pH8. The results of SAXS showed, that the Porod slope changed with chemical crosslinking time from -3.5 to -2.9 at pH4, and from -2.9 to -2.4 at pH8. The results suggest that a folded structure as a structural domain, which is characterized by fractally rough interface, tends to change into the structure that corresponds to percolation cluster, particularly at pH8. The gels immersed in pH8 showed a remarkable structure change accompanying swelling. The results revealed that a conformational change of PAA chains, induced by the pH change, can be explained by the presence of a structural domain in the gel network, where both PVA chains and PAA chains get entangled and partially form a interpenetrating polymer network(IPN).
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  • 64
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyurethane elastomers were investigated as electrically active materials for actuators. Components in hard segment and soft segment in the elastomers were varied. The elastomers with excellent electrostrictive properties were limited to those which had soft segments of polyesters and polylactones. It turned out, that the elastomers, whose soft segments are polyethers are electrically inert under the experimental conditions. The chemical structure of the hard segment seems not to influence to the electrostrictive property. The charging and discharging process was investigated. The charging process was found to proceed simultaneously with the contracting process caused by the electric field, suggesting that the orientation of the soft segment in the elastomer plays critical rolls in the electrostrictive action. In the elastomer, which has a soft polyether segment and was inactive to the electric field, could be actuated very efficiently when the elastomer was swollen with dimethyl sulfoxide. We conclude that the polyurethane elastomer, whose soft segment has chemical bonds with a relatively large dipole moment, can be actuated by the electric field application, and that even the elastomer, whose soft segment is inactive, could be actuated in the presence of a solvent with a large dipole moment. Thus, the concept found with the gel, could be applied to an elastomer, the soft segment of which plays partly the roll of the solvent in the gel.
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  • 65
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    Angewandte Makromolekulare Chemie 240 (1996), S. 263-273 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chitosan and 6-O-glycolchitosan, a water-soluble chitosan derivative, were oxidized by periodate. In the case of chitosan, only degradation products were obtained. With 6-O-glycolchitosan, however, water-soluble amphoteric polyelectrolyte derivatives of chitosan having higher molecular weight were obtained. The oxidized 6-O-glycolchitosan (OX-GC) showed a pH sensitive change of viscosity in aqueous solution. Moreover, the OX-GC hydrogel, cross-linked with glutaraldehyde, showed a pH sensitive swelling behavior. The OX-GC showed biodegradation behavior by lysozyme after acetylation.
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    Angewandte Makromolekulare Chemie 241 (1996), S. 11-29 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Fließ- und Bruchverhalten eines durch das gleichzeitige Härten eines ungesättigten Polyesters (UP) und eines wärmehärtbaren Bismaleimidharzes (BMI) erhaltenen quervernetzten Polymernetzwerkes wurde über einen weiten Temperatur- und Beanspruchungsbereich untersucht. Die Fließspannung σy und der Youngsche Elastizitätsmodul E steigen bei Zunahme der Spannungsbeanspruchung bzw. bei Absinken der Temperatur. Zudem steigen bei ansonsten gleichen Testbedingungen σy und E mit zunehmendem BMI-Gehalt im Blend. Andererseits wurde eine Beeinflussung des Bruch-Parameters Kc durch die Gegenwart des BMI nicht beobachtet. Der Fließprozess wurde sowohl mit Hilfe der Theorie von Argon als auch mit der von Bowden untersucht; die daraus abgeleiteten Molekül-Parameter wurden mit der bei der Härtung gebildeten Molekularstruktur in Beziehung gesetzt.
    Notes: The yielding and the fracture behaviour of an intercrosslinked polymer network obtained by the simultaneous curing of an unsaturated polyester (UP) and a thermosetting bismaleimide resin (BMI) was investigated in a wide range of temperatures and testing rates. The yield stress σy and the Young's modulus E increase by increasing the testing rate and decreasing temperature. Moreover, under the same testing conditions, σy and E increased as the BMI content in the blend was enhanced. On the other hand, it was found that the fracture parameter Kc was not affected by the presence of BMI. The yielding process was analyzed using the theories both of Argon and Bowden and the molecular parameters derived there were related to the molecular structure of the network developed upon curing.
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  • 67
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    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 242 (1996), S. 159-169 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Dicarbonsäuredichloride mit sowohl Hexafluorisopropyliden-Brücken und Imidringen im Molekül wurden mit p-Aminobenzhydrazid oder Mischungen aus aromatischen Diaminen und p-Aminobenzhydrazid oder Terephthaldihydrazid zu Poly(hydrazidimid-amid)en umgesetzt, die anschließend zu neuen fluorhaltigen Poly(1,3,4-oxadiazol-imid-amid)en mit verschiedenem Amid/Oxadiazol-Verhältnis cyclodehydriert wurden. Diese sind in polaren amidischen Lösungsmitteln löslich; aus solchen Lösungen lassen sich flexible Filme herstellen. Die Glasübergangstemperaturen liegen zwischen 254°C und 325°C. Sie sind bis zu 415-450°C thermisch stabil.
    Notes: A series of new fluorinated poly(1,3,4-oxadiazole-imide-amide)s containing various ratios of amide/oxadiazole groups in the repeating unit have been prepared by cyclodehydration of the corresponding poly(hydrazide-imide-amide)s resulting from the reaction of diacid dichlorides incorporating both hexafluoroisopropylidene bridges and imide rings with p-aminobenzhydrazide or with mixtures of certain aromatic diamines and p-aminobenzhydrazide or terephthalic dihydrazide. The new polymers are soluble in polar amidic solvents and can be processed into flexible films by casting from solution. Their glass transition temperatures are in the range 254-325°C and they are thermally stable up to 415-450°C.
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  • 68
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Blockcopoly(ester-ether) mit verschiedenen ionischen Einheiten wie Sulfobetain (S-Betain), Carbobetain (C-Betain) und Ammoniumtosylat wurden hergestellt und hinsichtlich ihrer Eignung als antistatische Modifikatoren für Polyethylenterephthalat (PET)-Fasern untersucht. Die ionischen Segmente wurden aus N,N-Bis(2-hydroxyethyl)methylamin generiert und statistisch mit den Polyester- und Polyoxyethylen(PEO)-Einheiten cokondensiert. Aus den Copolymeren mit S-Betain-Einheiten wurden im Schmelzspinnverfahren dicke Filamente hergestellt und deren elektrischer Widerstand bestimmt. Abhängig von der Zusammensetzung (25-75 Gew.-% PEO, 1-2 mol-% S-Betain) wurden Widerstände zwischen 108 und 1010 Ω cm-1 gemessen. Die drei copolymerartigen Modifikatoren wurden mit PET durch Blendspinnen gemischt. Die so erhaltenen PET-Fasem zeigen nicht nur gute mechanische sondern auch verbesserte antistatische Eigenschaften. Die Fasern aus dem S-Betain enthaltenden Copolymeren weisen dabei die kürzeste Halbwertszeit des Abbaus der elektrostatischen Ladung auf, obwohl der Oberflächenwiderstand dieses Materials in der Größenordnung 1013 Ω cm-2 dem Wert der mit C-Betain und Ammoniumtosylat hergestellten Fasem ähnlich ist. Die PET-Fasern bewahren ihre guten antistatischen Eigenschften auch nach dem Fäben und wiederholtem Waschen, da sowohl die hydrophilen als auch die ionischen Gruppen an den Polyesterketten fixiert sind.
    Notes: Block copoly(ester-ether)s containing different ionic units, i.e., sulfobetaine (S-betaine), carbobetaine (C-betaine), and ammonium tosylate, were prepared and evaluated as antistatic modifiers of PET fiber. The ionic units were readily derived from N,N-bis(2-hydroxyethyl)methylamine and co-condensed randomly with the polyester and poly(oxyethylene) (PEO) units. For the copolymers containing S-betaine units, a thick filament was melt-spun to evaluate their apparent electric resistivity. Depending on the unit compositions (25-75 wt.-% of PEO and 1-2 mol-% of S-betaine), resistivities ranging from 108 to 1010 Ω cm-1 were obtained. Then, the three copolymer-type modifiers were blended with poly(ethylene terephthalate) (PET) by the ordinary blend-spinning technique. The blend PET fibers obtained showed not only good mechanical properties, but also improved antistatic properties. Particularly, the fiber blended with the copolymer containing S-betaine units had the shortest half-life time of leakage of static charge, although the surface area resistivity, being in the order of 1013 Ω cm-2, was similar to that of the fibers blended with the copolymers containing C-betaine and ammonium tosylate units. These blend PET fibers were found to retain good antistatic properties even after dyeing and repeated washings, because both the hydrophilic and ionic groups are immobilized with the polyester chains.
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  • 69
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: For radical copolymerizations of α-methylstyrene (MS) with methacrylonitrile (MAN) and of MS with acrylonitrile (AN) studies were carried out to examine postulations of kinetic models known from literature, in particular the terminal model with chain-length-independent and chain-length-dependent depolymerization steps. The results of investigations were based on measurements of the sequence length distributions from 13C-NMR spectra. Analyses of MS/MAN copolymers with various compositions were carried out. Reaction parameters and depolymerization constants depending on temperature were calculated. The values of enthalpy and entropy of polymerization and the ceiling temperature were computed for MS to ΔH = 26,5 ± 0,5 kJ mol-1, ΔS = 95 ± 5 J mol-1 K-1, Tceiling = 65 ± 1°C. The terminal model with depolymerization steps turned out to be wrong for the accurate description of the polymerization behaviour in case of the tested systems. Results clearly show important penultimate effects. At the point of knowledge, the description of the polymerization behaviour in terms of a penultimate model with depolymerization steps are suggested.
    Notes: Für die radikalischen Copolymerisationen von α-Methylstyrol (MS) mit Methacrylnitril (MAN) sowie MS mit Acrylnitril (AN) wurden Untersuchungen zur Prüfung der in der Literatur postulierten kinetischen Modelle des „sequenzlängenunabhängigen“ bzw. „sequenzlängenabhängigen“ Terminalmodells mit Depolymerisationsschritten durchgeführt. Sie basieren auf Analysen der Sequenzverteilungen aus 13C-NMR-Spektren. Resultate von 13C-NMR-Untersuchungen an MS/MAN-Polymeren variabler Zusammensetzung werden vorgestellt. Reaktionsparameter und Gleichgewichtskonstanten wurden direkt aus den Informationen der 13C-NMR-Spektren für das Terminalmodell mit Depolymerisationsschritten in Abhängigkeit von der Reaktionstemperatur der Polymeren bestimmt. Hieraus konnten die Polymerisationsenthalpie ΔH = 26,5 ± 0,5 kJ mol-1, die Polymerisationsentropie ΔS = 95 ± 5 J mol-1 K-1 sowie die Ceilingtemperatur Tceiling = 65 ± 1°C für MS bestimmt werden. Es wurde nachgewiesen, daß im Rahmen der Terminalnäherung auch mit Berücksichtigung von Depolymerisationseinflüssen keine adäquate Beschreibung des Copolymerisationsverhaltens im Falle der untersuchten Systeme möglich ist. Vielmehr konnten als Ergebnis der Untersuchungen sowohl in Copolymeren von MS mit AN als auch mit MAN signifikante Penultimate-Effekte nachgewiesen werden. Aufbauend auf diesen Ergebnissen wird die Anwendung eines auf einer Penultimate-Näherung basierenden Modells, welches auch das Gleichgewicht in den Wachstumsreaktionen von MS berücksichtigt, zur theoretischen Vorhersage des Copolymerisationsverhaltens vorgeschlagen.
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  • 70
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein auf Magnesiumoxid aufgebrachter Polytitazan-Cobalt (III)-Komplex diente als effektiver Katalysator für die Epoxidierung von cis-Cycloocten mit molekularem Sauerstoff bei Normaldruck in Gegenwart von Isobutyraldehyd als Reduktionsmittel. Nach XPS-Untersuchungen wird Cobalt (III) durch den mehrzähnigen Stickstoffliganden des Polytitazans stabilisiert. Bei 25°C beträgt der cis-Cycloocten-Umsatz nach fünf Stunden 95,2%, mit einer Selektivität von 100% für das cis-Cyclohexylenoxid. Der Katalysator Kann mindestens neun Mal ohne Aktivitätsverlust verwendet werden.
    Notes: Magnesium oxide supported polytitazane cobalt (III) complex is demonstrated as an effective catalyst for the epoxidation of cis-cyclooctene with molecular oxygen at atmospheric pressure in the presence of isobutyraldehyde as the sacrificial reductant. XPS data show that the high-valent cobalt (III) is stabilized by the multidentate nitrogen ligand of polytitazane. The conversion of cis-cyclooctene is as high as 95.2% with 100% selectivity to the cis-cyclooctene oxide at 25°C within 5 h. The catalyst can be used at least nine times without loss of its activity.
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  • 71
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    Angewandte Makromolekulare Chemie 243 (1996), S. 177-187 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird über die Gleichgewichts-Schmelzpunktsdepression von Polycarbonat aus Bisphenol A (PC) in Mischungen mit Poly-∊-caprolacton (PCL) berichtet. Hierzu wird ein Modell entwickelt, das den gekrümmten Verlauf der gemessenen Hoffman-Weeks-Plots zu erklären vermag. Es berücksichtigt die Konzentrationsinhomogenitäten, die mit fortschreitender Kristallisation an der Kristallwachstumsfront entstehen. Die gelegentlich beobachtete Schmelzpunktsdepression der PCL-Komponente wird diskutiert. Der Flory-Hugginssche Wechselwirkungsparameter wird zu -0,09 berechnet; aus diesem kleinen Wert muß geschlossen werden, daß die Mischungspartner enthalpisch nur schwach wechselwirken. Der merkliche Abfall der Glastemperatur des PC nach Einmischen von PCL bewirkt eine beträchtliche Kristallisation aus der Schmelze; es können PC-Kristallinitätsgrade bis zu 25% erreicht werden.
    Notes: It is reported on the equilibrium melting point depression of polycarbonate from bisphenol A (PC) in its blend with poly-∊-caprolactone (PCL). To this end, a model which explains the bended course of the measured Hoffman-Weeks plots is developed which takes into account the composition changes at the crystal growth front upon progressive crystallization. The occasional melting point depression of the PCL component is discussed. The calculated Flory-Huggins parameter of χ12 ≍ -0.09 indicates only weak enthalpic interactions. The remarkable drop in the glass transition temperature of PC with blending allows PC degrees of crystallinity up to 25% upon crystallization from the melt.
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  • 72
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    Angewandte Makromolekulare Chemie 231 (1995), S. 199-211 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: 2-Methylaziridin (MAz) wurde als nukleophiles Monomeres mit den elektrophilen Monomeren Acrylsäure (AA) bzw. Methacrylsäure (MA) in unterschiedlichen Verhältnissen ohne Initiator copolymerisiert. Die Copolymeren wurden mittels Elementaranalyse, FT-IR- und 1H-NMR-Spektroskopie charakterisiert. Die Copolymerisationsparameter wurden mit den Methoden nach Fineman-Ross bzw. Kelen-Tüdős bestimmt. Für r1 und r2 wurden die Copolymerpaare MAz-AA und MAz-MA jeweils Werte 〈 1 ermittelt, was auf statistische Copolymere mit einer Tendenz zu alternierenden Copolymeren hinweist. Thermische Zersetzung mit einem Gewichtsverlust von 10% tritt bei den Copolymeren erst oberhalb 430 K auf. Der thermische Abbau verläuft nach einer Reaktion nullter Ordnung. Die kinetischen Parameter der Zersetzung der Copolymeren wurden bestimmt.
    Notes: 2-Methylaziridine (MAz) as a nucleophilic monomer and acrylic acid (AA) and methacrylic acid (MA), respectively, as electrophilic monomers were copolymerized in the absence of initiator at various feed ratios. Copolymers were characterized by elemental analysis, FT-IR and 1H-NMR spectroscopy. The monomer reactivity ratios were determined by the Fineman-Ross and Kelen-Tüdős methods. Values of r1 and r2 were found to be less than unity for MAz-AA, and MAz-MA, corresponding to random copolymers with the tendency to the alternance. For all the copolymers the thermal decomposition with 10% weight loss is higher than 430 K. The reaction order for degradation of all copolymers was zero. The kinetic parameters of the decomposition were determined for all copolymers.
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  • 73
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanism of the solid state oxidation of isotactic polypropylene films and the the mechanism of inhibition by HALS have been investigated by kinetic-ESR and kinetic modelling with derivation of the rate constants for the sensitive steps in the reaction scheme. The results have shown the inadequacy of the Denisov cycle to account for the observed experimental kinetics of the intermediate nitroxyl radicals. The molecular dynamics associated with the oxidation inhibited by HALS in the polypropylene matrix has been investigated by applying the Liouville stochastic method to the analysis of the temperature effects of the ESR spectra of the intermediate nitroxyl radicals used as spin probes. The investigation on the nature and characteristics of the molecular motions available at the oxidation sites has also been carried out with nitroxyl spin labels bound to the PP chains. For this application a novel method of spin labelling was developed based on reactions with some of the oxidation products, namely the terminal and intrachain ketones (keana method), alcohols, peroxides and macroalkyl radicals.
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  • 74
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: As plastics are being used in a variety of applications, demands on a greater level of processing stability are increasing. Phosphites are noteworthy as effective processing stabilizer and the performance of phosphite antioxidants can be correlated to the chemical structure of phosphites. Cyclic phosphite esters derived from 2, 2′ methylene bis-2, 4-di-tert-butylphenol and some commercially available phosphites were submitted to comparative studies. Decomposition of cumene hydroperoxide, melt flow of polypropylene and consumption of additives after multiple extrusions were investigated to understand the activity of phosphites as process stabilizers in polypropylene.This study suggests that phosphites play an important role in process stabilization when used in combination with sterically hindered phenols, and that the activity of phosphites may be predicted by their reactivity on hydroperoxide.
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  • 75
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    Angewandte Makromolekulare Chemie 243 (1996), S. 151-159 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Leicht vernetzte Hydrogele auf der Basis von Acrylamid, N-(1,1-Dimethyl-3-oxobutyl)acrylamid, N,N-Dimethylacrylamid, Methacrylamid, N-(2-Hydroxypropyl)-methacrylamid und N-[Tris(hydroxymethyl)methyl]methacrylamid wurden in Form von pulverigen Substanzen synthetisiert, die aus Aggregaten sehr kleiner Partikel (∼10-1 μm) bestehen. Die pulverartigen Hydrogele wurden durch Fällungspolymerisation in Aceton und Diethylether unter Verwendung von N,N′-Methylenbisacrylamid und Ethylendimethacrylat als Vernetzungsmittel synthetisiert. Es wurden die Abhängigkeiten des Quellungsgrades in Wasser, der Größe, des Aggregationsgrades und der spezifischen Oberfläche von Partikeln, und des Inhalts von wasserlöslichen Substanzen in den Hydrogelen von den Bedingungen ihrer Synthese verfolgt. Die Eignung einzelner der synthetisierten Hydrogele für die Herstellung von Silikon-kautschuk-Hydrogel-Kompositen wird diskutiert.
    Notes: Lightly crosslinked hydrogels based on acrylamide, N-(1,1-dimethyl-3-oxobutyl)-acrylamide, N,N-dimethylacrylamide, methacrylamide, N-(2-hydroxypropyl)methacrylamide and N-[tris(hydroxymethyl)methyl]methacrylamide were synthesized in form of fine powders, consisting of aggregates of very small (∼10-1 μm) particles. The powdery hydrogels were obtained by precipitation polymerization in acetone and diethyl ether, using N,N′-methylenebisacrylamide and ethylene dimethacrylate as crosslinking agents. Dependences of water-swellability, particle size, aggregation, specific surface and content of the uncrosslinked water-soluble polymers and low-molecular-weight substances in the hydrogels on the conditions of their synthesis were studied. Suitability of particular powdery hydrogels synthesized for the preparation of silicone rubber-hydrogel composites is discussed.
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  • 76
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde der Einfluß der Polymerisationsbedingungen auf die Eigenschaften von Poly(∊-Caprolactam)-Polybutadien-Blockcopolymeren untersucht, die durch Reaktionsformgießen bei der anionischen ∊-Caprolactam-Polymerisation, initiiert durch das ∊-Caprolactam-Kaliumsalz, in Anwesenheit von α,ω-Dihydroxypolybutadien und Isocyanaten oder deren blockierter Derivate als Funktionalisierungsmittel hergestellt wurden.Es wurde der Einfluß des Polybutadiengehalts, dessen Molekulargewichts, des Isocyanat-Typs und der Polymerisationstemperatur auf die mechanischen Grundeigenschaften und auf die Polymerisationsgeschwindigkeit bestimmt.
    Notes: The effect of the polymerization conditions on the properties of poly(∊-caprolactam)-polybutadiene block copolymers prepared by polymerization casting through anionic polymerization of ∊-caprolactam initiated with potassium salt of ∊-caprolactam in the presence of α,ω-dihydroxy-polybutadiene and isocyanates or their blocked derivatives as functionalizing agents was investigated.The influence of the content of telechelic polybutadiene, its molecular weight, type of diisocyanate, and polymerization temperature on the fundamental mechanical properties of the prepared materials and on the polymerization rate was evaluated.
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  • 77
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    Angewandte Makromolekulare Chemie 238 (1996), S. 55-62 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Tetrahydrofuran (THF) wurde mit dem Initiatorsystem 4,4′-Azobis(4-cyanopentanoylchlorid)/SnCI4 kationisch polymerisiert. Das gebildete Poly(THF) mit je einer Azogruppe in der Hauptkette wurde als Initiator für die Polymerisation von Styrol (S) und Methylmethacrylat (MMA) bei 70°C eingesetzt. Die dabei entstandenen PTHF-PS-PTHF- bzw. PTHF-PMMA-Blockcopolymeren wurden mittels Fällungsfraktionierung, spektroskopischen Methoden und Viskositätsmessungen charakterisiert.
    Notes: The cationic polymerization of tetrahydrofuran (THF) initiated by 4,4′-azobis(4-cyanopentanoyl chloride) (ACPC) and SnCI4 is described. Poly(THF) samples possessing azo gorups in the main chain thus obtained were used as initiator in the polymerization of styrene (S) and methyl methacrylate (MMA) at 70°C to yield PTHF-PS-PTHF and PTHF-PMMA block copolymers. Characterization of the block copolymers was carried out by fractional precipitation, spectroscopic methods and viscosity measurements.
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  • 78
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    Angewandte Makromolekulare Chemie 238 (1996), S. 129-141 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Wirkung von aliphatischem Korrosionsschutzöl auf das Aushärte- und Abbauverhalten eines ölkompatiblen Epoxidharzklebers wurde mittels Differentialkalorimetrie (DSC), Fourier-Transformations-Infrarot-Spektroskopie (FTIR) und Thermogravimetrie (TGA) untersucht. Die Ergebnisse der DSC- und FTIR-Messungen deuten darauf hin, daß die Härtungsgeschwindigkeit des untersuchten Epoxid-Systems durch das Vorhandensein des Öls nur wenig beeinflußt wird. Dennoch bestätigt das Absinken der exothermen Härtungskurve, begleitet von einer Verbreiterung des Glasübergangstemperaturbereichs, daß das Öl den Aushärtemechanismus beeinflussen kann und in der Lage ist, die Struktur des gehärteten Harzes zu verändern. Außerdem geht aus den TGA-Messungen hervor, daß die Temperaturbeständigkeit des Harzes sich in Gegenwart des Öls verschlechtert; dies wird auf Veränderungen in der Struktur und im Abbaumechanismus des Epoxid-Systems zurückgeführt.
    Notes: The effect of aliphatic slushing oil on the curing and degradation behavior of an oil-accommodating epoxy adhesive is studied by using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The results of FTIR and DSC indicate that the curing rate of the tested epoxy system is little affected in the presence of the oil. However, the decrease of the curing exotherm accompanied with a broadening of the glass transition confirms that the oil can affect the curing mechanisms and may change the structure of the cured resin. Additionally, it is evident from the TGA results that the thermal resistance of the resin deteriorates in the presence of the oil, which is attributed to the changes in the structure and the degradation mechanism of the epoxy system.
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  • 79
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    Angewandte Makromolekulare Chemie 239 (1996), S. 1-12 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die elektrochemische Polymerisation von Pyrrol-2-aldehyd-azin, 2,2′-[1,4-Phenylenbis(nitrilomethylidyn)]dipyrrol und 2,2′-[1,4-Biphenylylenbis(nitrilomethylidyn)]dipyrrol läuft als anodische Fällungspolymerisation ab. Monomere und Polymere wurden voltammetrisch unter Verwendung von Platin- und “Paste-carbon”-Elektroden untersucht. Die Ergebnisse stimmen mit MO-Berechnungen überein, wobei die Reaktivität der Monomeren nach Hückel abgeschätzt wurde.
    Notes: The electrochemical polymerization of some Schiff's base-type monomers like pyrrole-2-aldehyde azine, N,N′-di(2-pyrrolylmethylene)-1,4-diaminobenzeneSystematic name: 2,2′-[1,4-phenylenebis(nitrilomethylidyne)]dipyrrole., and N,N′-di(2-pyrrolylmethylene)-4,4′-diaminobiphenylSystematic name: 2,2′-[4,4′-biphenylylenebis(nitrilomethylidyne)]dipyrrole. proceeds as a precipitating polymerization to the anodic compartment. The voltammetric study of monomers and polymers using Pt electrodes and paste-carbon electrodes were carried out. The results are in agreement with the MO calculations using the Hückel approximation for evaluating of the reactivity of the monomers.
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  • 80
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    Angewandte Makromolekulare Chemie 239 (1996), S. 33-41 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der neuartige dikationische Komplex [dppfNi(MeCN)4][BF4]2 (dppf = 1,1′-Bis(diphenylphosphin)ferrocen) zeigte in Anwesenheit von Diethylaluminiumchlorid (AIEt2CI) hohe Aktivität für die Polymerisation von 1,3-Butadien. Reaktionsdauer, Temperatur und das Aluminium/Nickel-Verhältnis wurden auf maximale Aktivität und Selektivität optimiert. Umsätze über 90% konnten erreicht werden. Im Vergleich zu Polybutadienen, die mit anderen Nickel-Phosphin-Systemen hergestellt wurden, zeigten die synthetisierten Polybutadiene höhere cis-1,4-Anteile (〈80%) und eine geringe Bildung von 1,2-Einheiten (2%). Alle Polymeren hatten niedrige mittlere Molekulargewichte (Mw 〉 11 800).
    Notes: The new dicationic nickel complex [dppfNi(MeCN)4][BF4]2 (dppf = 1,1′-bis(diphenylphosphino)ferrocene) in the presence of diethylaluminium chloride (AIEt2CI) exhibited high activity on the 1,3-butadiene polymerization. Reaction time, temperature and aluminium/nickel molar ratio were optimized in order to achieve maximum activity and selectivity. Conversions higher than 90% were obtained in contrast to other nickel-based systems using phosphine ligands, the resulting polybutadiene showed high cis-1,4 (〈80%) content and only small amount of 1,2-units (2%). All polymers presented low molecular weights (Mw 〉 11 800).
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  • 81
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bei der Bestrahlung von Polymethylmethacrylat (PMMA) mit Röntgensynchrotronstrahlung ändert sich die chemische Struktur des Polymeren. Die Ergebnisse der analytischen Untersuchungen dieser Arbeit weisen darauf hin, daß neben einem Abbau der Polymerketten auch einzelne Esterseitengruppen abgespalten werden. Durch die Bestrahlung entstehende Langkettenverzweigungen wurden bei PMMA nicht gefunden. Dadurch unterscheiden sich die physikalischen und chemischen Eigenschaften des bestrahlten Polymeren von denen des unbestrahlten.
    Notes: The irradiation of poly(methyl methacrylate) changes the chemical constitution of the polymer. In addition to a decrease in molar mass further radiation-induced radical reactions cause changes in the chemical constitution of the polymer. Analysis of the reaction products shows that formation of long-chain branching can be excluded. Along with degradation of the chain lengths, ester groups in the side chains are attacked. The result is a modified polymer with a physical and chemical behaviour different from that of the starting polymer.
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  • 82
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    Angewandte Makromolekulare Chemie 239 (1996), S. 133-149 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Zähigkeit von Polyarylaten wurde durch den Einbau von 4,4′-Thiodiphenol und Bisphenol A, die in der wäßrigen Phase einer Grenzflächenpolykondensation vorgelegt wurden, erhöht. Die modifizierten Polyarylate besitzen leicht erniedrigte Zugfestigkeiten und Zugmoduli, aber aufgrund der Flexibilität der eingebauten Segmente stark erhöhte Izod-Schlagzähigkeiten. Darüber hinaus bleiben die guten thermischen Eigenschaften der Polyarylate nach der Modifizierung erhalten, so daß die hergestellten Materialien auch für Anwendungen mit sehr hohen Anforderungen an die thermische Belastbarkeit geeignet sind.
    Notes: The toughness of polyarylates was improved by incorporation of 4,4′-thiodiphenol and bisphenol A, being introduced in the aqueous phase of an interfacial polycondensation reaction. The modified polyarylates possessed slightly lower tensile strength and modulus but much higher Izod impact strength due to the flexibility of the incorporated segments. In addition, the superb thermal properties typical for polyarylates were reserved in the modified polyarylate, thus assuring its broad applicability for those applications where extremely stringent criteria of thermal characteristics are required.
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  • 83
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The photocrosslinking efficiency of a series of commercial photoinitiators and multicomponent photosensitive systems on uncrosslinked acrylic matrices has been estimated. Copolymers used for this study are tricyclo[5.2.1.02,6]dec-4-en-8-yl acrylate/ethyl acrylate copolymers of variable composition (100/0, 40/60, 20/80, 0/100) synthesized in solution by a free-radical process. The irradiations were carried out at large wavelengths (λ ≥ 310 nm). Systems of benzophenone/benzoyl peroxide led to really fast crosslinking kinetics for 10 min of irradiation.
    Notes: L'efficacité de photoréticulation de toute une série de photoamorceurs commerciaux et de systèmes photosensibles multicomposants a été évaluée sur des matrices acryliques non réticulées. Les polymères utilisés pour cette étude sont des homopolymères et des copolymères d'acrylate de dicyclopentadiène/acrylate d'éthyle de composition variable (100/0, 40/60, 20/80, 0/100) synthétisés en solution par voie radicalaire. Les irradiations ont été effectuées à des grandes longueurs d'ondes (λ ≥ 310 nm). Les systèmes benzophénone/peroxyde de benzoyle ont permis d'obtenir des cinétiques de réticulation très rapides pour des temps d'irradation de 10 min.
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  • 84
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The critical conditions in which the classical Flory-Stockmayer gelation theory (F-S theory) is applicable to monovinyl-divinyl copolymerizations were pursued in detail. The resulting prepolymers or precursors of ideal crosslinked-polymers were characterized as standard polymers for the discussion of network formation in free-radical monovinyl-divinyl copolymerizations. Methyl methacrylate was copolymerized with a small amount of ethylene dimethacrylate, butylene dimethacrylate or nonapropyleneglycol dimethacrylate in the presence of lauryl mercaptan, a chain transfer agent to reduce the occurrence of a thermodynamic excluded volume effect and intramolecular crosslinking as the primary and secondary factors, respectively, for the greatly delayed gelation in the free-radical monovinyl-divinyl copolymerizations and, moreover, to keep the primary chain length constant by inhibiting a gel effect. The ratio of the actual gel point to the theoretical one reached 1.1, supporting the validity of F-S theory. The resulting prepolymers were subjected to SEC-MALLS analysis to determine the molecular weights, the molecular-weight distributions and the radii of gyration; the correlations of molecular weight vs. elution volume and radius of gyration vs. molecular weight were useful for the characterization of the precursors of ideal network-polymers.
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  • 85
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Reaktion von Mesylchlorid mit vernetzten Pullulan-Mikropartikeln wurde untersucht, insbesondere der Einfluß der Reaktionsbedingungen auf das Produktverhältnis Chlordeoxy-/O-Mesylpullulan. In N,N-Dimethylformamid wird vorwiegend Chlordeoxypullulan gebildet, während in Pyridin bei niedrigen Temperaturen der Mesylester das Hauptprodukt ist. In N,N-Dimethylacetamide entstehen Chlordeoxy und Mesylgruppen im Verhältnis 2:1. Durch die Einführung der Chlordeoxy- bzw. Mesylgruppen werden die Mikropartikel hydrophob.
    Notes: The reaction of mesyl chloride with crosslinked pullulan microparticles was investigated, in particular the influence of the reaction conditions on the ratio between the two possible products chlorodeoxy or O-mesyl pullulan. It was found that in N,N-dimethylformamide the preponderent reaction product is chlorodeoxy pullulan, while in pyridine at low temperatures the main product is the mesyl ester of pullulan. In N,N-dimethylacetamide, the substituent groups are both chlorodeoxy and mesyl ones, in about 2:1 ratio. By the introduction of either chlorodeoxy or mesyl groups, the pullulan-crosslinked microparticles become hydrophobic.
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  • 86
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    Angewandte Makromolekulare Chemie 241 (1996), S. 41-56 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(4-hydroxybutylacrylat) poly(4-HBA) wurde aus wäßrigem Medium mit Ammoniumpersulfat als Initiator auf Seide (bombyx mori) aufgepfropft. Die Gewichtszunahme stieg proportional mit der Monomerkonzentration im Pfropfsystem. Der Pfropfgrad lag im Bereich von 45 bis 65%. Die Feuchtigkeitsaufnahme nahm bei einer Gewichtszunahme von 〉10% stark ab. Die mechanischen Eigenschaften der Seidenfasern zeigten mit steigender Gewichtszunahme keine wesentliche Änderung. Doppelbrechung und isotroper Brechungsindex nahmen bis zu einer Gewichtszunahme von 35% ab und blieben dann unverändert. Röntgenbeugungsdiagramme zeigten, daß die kristalline Struktur durch die Pfropfbehandlung nicht modifiziert wird. Kalorimetrische (DSC), thermomechanische (TMA) und thermogravimetrische (TG) Analysen ergaben, daß das thermische Verhalten der poly(4-HBA)-gepfropften Seidenfasern nur leicht verändert wird. Die zur Bestimmung des dynamisch-mechanischen Verhaltens der Seidenfasern durchgeführten DMA-Messungen zeigten eine Verschiebung der E′- und E″-Modulspitzen zu niedrigeren Temperaturen mit steigender Gewichtszunahme. Ablagerungen auf der Faseroberfläche der bei einem hohen Monomer/Seide-Verhältnis (〉50%) gepfropften Seide wurden mit Rasterelektronenmikroskopie nachgewiesen.
    Notes: Poly(4-hydroxybutyl acrylate) poly(4-HBA) was graft-copolymerized onto silk fibres (bombyx mori) in aqueous medium with ammonium persulfate as initiator. The weight gain increased with increasing concentration of monomer in the grafting system. The grafting efficiency ranged from 45 to 65%. Equilibrium moisture regain decreased sharply beyond 10% weight gain. The tensile properties of the silk fibres did not change significantly as a function of the increasing weight gain. Birefringence and isotropic refractive index decreased until 35% weight gain and then remained unchanged. The X-ray diffraction patterns showed that the crystalline structure was not affected by grafting. Differential scanning calorimetry (DSC), thermomechanical (TMA), and thermogravimetric (TG) measurements showed that poly(4-HBA)-grafted silk fibres underwent only slight changes in the thermal behaviour. The dynamic mechanical measurements (DMA) exhibited a downward shift of both the storage (E′) and loss modulus peak (E″) with increasing weight gain. Scanning electron microscopy (SEM) observations showed the presence of some deposits adhering to the surface of silk fibres grafted at high monomer/silk ratio (〉50%).
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  • 87
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal state conformations of three peptides containing the α,α-dialkylated residues. α,α-di-n-propylglycine (Dpg) and α,α-di-n-butylglycine (Dbg), have been established by x-ray diffraction. Boc-Ala-Dpg-Alu-OMe (I) and Boc-Ala-Dbg-Ala-OMe (III) adopt distorted type II β-turn conformations with Ala (1) and Dpg/Dbg (2) as the corner residues. In both peptides the conformational angles at the Dxg residue (I: φ = 66.2°, ψ = 19.3°; III: φ = 66.5°. ψ = 21.1°) deviate appreciably from ideal values for the i + 2 residue in a type II β-turn. In both peptides the observed (N…O) distances between the Boc CO and Ala (3) NH groups are far too long (1: 3.44 Å: III: 3.63 Å) for an intramolecular 4 → 1 hydrogen bond. Boc-Ala-Dpg-Ata-NHMe (II) crystallizes with two independent molecules in the asymmetric unit. Both molecules HA and HB adopt consecutive β-turn (type III-III in HA and type III-I in IIB) or incipient 310-helical structures, stabilized by two intramolecular 4 → 1 hydrogen bonds. In all four molecules the bond angle N-Cα-C′ (τ) at the Dxg residues are ≥ 110°. The observation of conformational angles in the helical region of φ,ψ space at these residues is consistent with theoretical predictions. © 1995 John Wiley & Sons, Inc.
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  • 88
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of the protected seven-residue C-terminal fragment the lipopeptaibol antibiotic Trichogin A IV (Boc-Gly-Gly-Leu-Aib-Gly-Ile-Leu-OMe) has been examined in CDCl3 and (CD3)2SO by 1H-nmr. Evidence for a multiple β-turn conformation [type I′ at Gly(1)-Gly(2), type II at Leu(3)-Aib(4), and a type I′ at Aib(4)-Gly(5)] suggests that Leu(3) has preferred an extended or semiextended conformation over a helical conformation in CDCl3. This structure is thus in contrast to earlier observations of seven-residue peptides containing a single central Aib preferring helical conformations in both solution and crystalline slates. A structural transition to a frayed right-handed helix is absented in (CD3)2SO. These results suggest that nonhelical conformations may be important in Gly-rich peptides containing Aib. Further, the presence of amino acids with contradictory influences on backbone conformational freedom can lead to well-defined conformational transitions even in small peptides. © 1995 John Wiley & Sons, Inc.
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  • 89
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    Biopolymers 35 (1995), S. 31-46 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A statistical method based on classifying the transitions among a set of dihedral angles within an “energy transfer window” is developed, and used to analyze Brownian (BD) and molecular dynamics (MD) simulations of the acyl chains in a lipid bilayer, and MD of neat hexadecane. It is shown for the BD simulation that when a transition of the dihedral angle in the center of the chain occurs, a transition of a particular next nearest neighbor (or angle 2-apart) will follow concertedly with a probability of approximately 0.10 within a lime window of approximately 3 ps. The MD bilayer simulations, which are based on a more flexible model of the hydrocarbon chains, yield corresponding concerted transition probabilities of approximately 0.083 and window sizes of 1-2 ps. An analysis of angles 4-apart yields concerted transition probabilities of 0.03 and 0.04 for the BD and MD bilayer simulations, respectively, and window sizes close to those of the corresponding 2-apart cases. Statistical hypothesis testing very strongly rejects the assertion that these follower transitions are occurring at random. Similar analysis reveals marginal or no evidence of concertedness between 1-apart (nearest neighbor) and between 3-apart dihedral angle transitions. The pattern of concertedness for hexadecane is qualitatively similar to that of the lipid chains, although concertedness is somewhat stronger for the 3-apart transitions and somewhat weaker for those 4-apart. Finally, it is suggested that the diffusion of small solute molecules in membranes is better facilitated by non concerted transitions, which are associated with relatively large displacements of the chains, than by concerted transitions, which do little to change the chain shape. © 1995 John Wiley & Sons, Inc.
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  • 90
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    Biopolymers 35 (1995), S. 161-169 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using gravimetric and radiotracer techniques, we investigated the effects of mechanical stress, osmotic pressure, and temperature on the volumes of the intra- and extrafibrillar water spaces in arterial elastin. We also investigated the effects of temperature on water flow through elastin membranes and on dynamic mechanical properties of elastin rings. Compression by mechanical or osmotic loading reduced the hydration of the elastin in an identical manner. Two distinct stages were evident; at low loads there was extensive water removal from the extrafibrillar space while high loads were required to remove water from the intrafibrillar space. Conversely, dehydration caused by mechanical extension of the matrix was associated with a much smaller loss from the extrafibrillar compartment and a large fractional decrease in the intrafibrillar space. Contraction of the matrix as a result of increased temperature had similar effects on hydration to those produced by extension. Water flux across elastin membranes, corrected for changes in viscosity, and specific hydraulic conductivity both increased as a result of temperature-induced contraction. This effect was attributed to increases in both the fractional volume of the extrafibrillar space and the fiber radius. The elastic modulus decreased with increasing temperature, but there was an increase in viscoelasticity. Previous studies have determined that viscoelasticity depends on the rate of redistribution of intrafibrillar water, so this finding provides additional evidence that heating affects primarily the volume of the intrafibrillar space. © 1995 John Wiley & Sons, Inc.
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  • 91
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    Biopolymers 35 (1995), S. 211-216 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We used agarose gel electrophoresis to measure the effective charge neutralization of DNA by counterions of different structure and valence, including Na+, Mg2+, Co(NH3)63+, and sperinidine3+, which competed for binding with an excess of Tris acetate buffer. Linear DNA molecules ranged in size from 1 to 5 kilobases, and supercoiled plasmid pUC18 was also measured. In all cases, the results were in good agreement with theoretical predict ions from counterion condensation theory for two-counterion mixtures. © 1995 John Wiley & Sons, Inc.
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  • 92
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydrogen exchange rates of the backbone amide and labile side-chain protons of the dimeric Arc repressor have been measured. For the slowly exchanging amides in the α-helical regions, these rates show a concentration dependence. To account for this dependence, the role of the monomer-dimer equilibrium was considered. Extrapolating the observed exchange rates to zero dimer concentration provides estimates of these rates in the monomer and shows that they are significantly retarded compared to those of an unfolded polypeptide. This suggests that the monomer is in a structured “molten globule” like state. In particular, the two helices of Arc retain a high degree of their secondary structure and it is proposed that the two amphiphilic helices are packed together with their hydrophobic faces. Evidence for a partially folded structure in the Arc monomer was reported earlier in two other studies [J. L. Silva, C. F. Silveira, A. Correia, Jr., and L. Pontes (1992) Journal of Molecular Biology, Vol. 223, pp. 545-555: X. Peng, J. Jonas, and J. L. Silva (1993) Proceedings of the National Academy of Science USA, Vol. 90, pp. 1776-1780]. By combining the results of these studies and ours, a folding pathway of the dimeric Arc repressor involving four different stages is proposed. Due to the low concentration of Arc repressor in the cell, the protein is present either as a free monomer or it is bound to DNA presumably as a tetramer. Therefore the folding pathway can be regarded as an integral part of the overall DNA binding process. © 1995 John Wiley & Sons, Inc.
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  • 93
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    Biopolymers 35 (1995) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 94
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    Biopolymers 35 (1995), S. 289-296 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We used a Monte Carlo approach to compute the statistical properties of closed DNA chains with different descriptions of the electrostatic interactions. We compared these computed results with experimentally measured knotting probabilities, which are very sensitive to intersegment interactions. The calculated results based on the Debye-Hückel approximation of the solution of the Poisson-Boltzmann equation agreed very well with the published experimental data, while potential based on counterion condensation theory was clearly less satisfactory. We then compared the simpler hard-core approximation of electrostatic interactions to the Debye-Hückel potential. The hard-core approximation, specified in terms of a DNA effective diameter, gives the same conformational properties of random coils as the Debye-Hückel approximation. We found clear but relatively small differences between the two potentials for the conformational properties of supercoiled DNA. © 1995 John Wiley & Sons, Inc.
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  • 95
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Cd(II) complex of a peptide, Z-Cys-Ala-Pro-His-OMe was prepared and characterized by absorption, CD, 1H-, 13C-, and 113Cd-nmr, and nuclear Overhauser effect spectroscopy (NOESY) spectra to show the coordination of cysteine thiolate and histidine imizazole to Cd(II) ion. The NOESY spectra in dimethyl formamide showed that the cysteine residue was in proximity to the histidine residue. These results reveal the dictation of Z-Cys-Ala-Pro-His-OMe to Cd(II) ion in solution. Temperature-dependent dissociation equilibrium of histidine imidazole in solution was observed in this complex. Structural features of the chelating peptide are discussed. © 1995 John Wiley & Sons, Inc.
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  • 96
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dissolution of α-chymotrypsin in nonpolar organic solvents can be achieved using hydrophobic ion pairing, whereby the polar counterions are replaced by a stoichiometric number of detergent molecules. Using Aerosol OT[AOT, sodium bis(2-octyl)sulfosuccinate], it is possible to partition significant amounts of the enzyme into alkanes and chlorocarbons. Apparent solubility in isooctane is greater than 1 mg/mL (80 μM). Necessary conditions for achieving effective partitioning of α-chymotrypsin into these solvents are described. Using CD spectroscopy, it can be shown that the AOT-α-chymotrypsin (CMT) complex retains its native secondary and tertiary structure when dissolved in alkanes, and that the globular structure is stable to more than 100°C. In contrast, α-chymotrypsin unfolds at 54°C in aqueous solution. The relative solubility of the AOT-CMT complex in a variety of alkanes and chlorocarbons is also reported. The native structure of α-chymotrypsin is maintained in carbon tetrachloride, but not in methylene chloride or chloroform. © 1995 John Wiley & Sons, Inc.
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  • 97
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    Biopolymers 35 (1995), S. 475-483 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrolysis of β-lactoglobulin with thermolysin and pepsin at pressures ranging between 0.1 and 350 MPa showed a significant increase of cleavage rates. Pressure-induced changes of susceptibility to hydrolysis of β-lactoglobulin proteolytic sites were also observed. The pressure, raised to 200 MPa, accelerates the hydrolysis of β-lactoglobulin by thermolysin and changes obtained peptide profiles. Initially, higher pressure makes the N-terminal, and to a smaller extent, C-terminal peptide fragments of β-lactoglobulin molecule, more susceptible to removal by thermolysin. This indicates combined influence of pressure-induced thermolysin activation and partial unfolding of β-lactoglobulin by compression at neutral pHs.The rates of hydrolysis of β-lactoglobulin by pepsin (negligible at 0.1 MPa) are increased considerably with pressure up to 300 MPa. The Susceptibility of β-lactoglobulin proteolytic sites to peptic cleavage remains constant over all the studied pressure range. The lack of significant qualitative changes in the peptic peptide profiles produced at different pressures and at clearly pressure-dependent rates points to negative reaction volume changes as the major factor in peptic hydrolysis of β-lactoglobulin under high pressure. Thus the β-lactoglobulin molecule resists pressure-induced unfolding in acid pHs and yields to it in neutral pHs. © 1995 John Wiley & Sons, Inc.
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  • 98
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of competitive binding of two polyanions - DNA and synthetic fluorescence-tagged poly(methacrylate) (PMA*) - with the polycation-quencher poly(N-ethyl-4-vinyl-pyridinium) (PEVP) was studied by fluorescence quenching technique. It was found that ability of DNA to displace PMA *from the water-soluble nonstoichiometric interpolyelectrolyte complex (NPEC) formed by PMA* and PEVP - NPEC(PMA*-PEVP) - and to form water-soluble NPEC(DNA-PEVP) \documentclass{article}\pagestyle{empty}\begin{document}$$ NPEC(PMA^{*}\hbox{-}PEVP) + DNA \Leftrightarrow NPEC(DNA\hbox{-}PEVP) + PMA^{*}$$\end{document} can be determined by the parameter Ψ = PPMA*/PPEVP where PPMA* and PPEVP are the degrees of polymerization of PMA* and PEVP, respectively. In the case of Ψ 〈 1 the decrease of Ψ leads to the shift of the reaction equilibrium to the right, which can be explained by the gain of entropy due to the increase of the total number of polymeric particles in the solution. Introduction of alkali metal cations into the reaction mixture results in the shift of the reaction equilibrium, and according to their ability to shift the equilibrium to the right the cations can be arranged in the series Na+ 〉 K+ 〉 Li+. The substitution of native DNA by denatured DNA practically does not affect the reaction equilibrium in solutions of NaCl and KCl but considerably shifts it to the right in solutions of LiCl. The data obtained are in accordance with the differences in the selectivity of alkali cations binding with competitive polyanions. © 1995 John Wiley & Sons, Inc.
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  • 99
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    Biopolymers 35 (1995), S. 543-553 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report the design of hybrid molecules to bind in the minor groove of B-DNA, which combine DNA alkylating and cross-linking ability for increased chemotherapeutic efficacy, with sequence specificity, to minimize side effects. Optimal linkage geometries have been determined for the synthesis of bis-anthramycin and anthramycin-netropsin hybrid molecules. Earlier studies on linked drugs have typically been based on molecular mechanics calculations. This work, in contrast, uses the observed crystal structures of a netropsin/DNA complex and a new anthramycin/DNA complex to determine the exact spacing between two individual drugs when bound in the minor groove of B-DNA. Molecular linkers then are designed and tested between these two experimental positions, to form a chimeric or bis-linked compound molecule. A linked anthramycin-netropsin molecule has been designed specifically to target the polypurine tract second-strand primer site of the reverse transcriptase of HIV-1. © 1995 John Wiley & Sons, Inc.
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  • 100
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We carry out temperature-dependent lattice dynamics calculations to determine the vibrational normal modes associated with the interbase H-bond breathing motion in several B-DNA copolymers at temperatures from room temperature to the melting temperatures. We take into consideration Raman selection rules and incorporate a simple empirical model of Raman susceptibility in the interbase H bonds in our calculation and compare them to Raman measurements. Our calculations are carried out using empirical force constants that are not further refined to low-frequency spectra. Our calculations show the existence of strong interbase H-bond breathing modes at frequencies and with relative oscillator strengths close to the observed Raman peaks in the range of 60-140 cm-1 for the DNA sequences considered except for one helix. The correlation between the calculated and observed frequencies and oscillator strengths indicates that the observed Raman peaks in the frequency range are likely interbase H-bond breathing modes. We find that these modes exhibit sizable temperature as well as sequence dependence. We show the softening of these modes on approaching thermal denaturation that is also in agreement with the observed behavior in Raman and melting measurements. The sensitivity of the calculation on the empirical model of Raman susceptibility and the possible reasons for the discrepancy between a few calculated values and observations are discussed. © 1995 John Wiley & Sons, Inc.
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