bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oriented supramolecular systems‐polymeric monolayers and multilayers from prepolymerized amphiphiles
Authors: Laschewsky A. , Ringsdorf H. , Schneider J. 
Published: April 2003

AbstractOriented polymeric membranes were originally prepared by polymerization or polycondensation of preoriented monomers. The introduction of hydrophilic spacer groups into the polymeric amphiphiles allowed the formation of highly ordered systems (monolayers, liposomes, multilayers) from prepolymerized amphiphiles: due to the partial decoupling of the different mobilities and orientation tendencies of the polymer chain and the amphiphilic side groups, these polymers are able to self‐organize. In monolayer experiments the high order of these membranes could be demonstrated by their surface pressure area‐diagrams. In addition the combination of order and mobility of these spacer groups containing polymeric amphiphiles allowed the formation of Langmuir‐Blodgett‐multilyers with a high layer correlation. Thus, disturbancies in highly oriented layers can be avoided normally taking place during the polymerization reaction (e.g. contractions) or oriented monomeric layers.
Telechele als bausteine für neuartige polymere
Authors: Heitz Walter 
Published: April 2003

AbstractThe developments in the syntheses of α,ω‐bifunctional oligomers (telechelics) are revued. Telechelic soft segments are synthesized by cationic, anionic and radical polymerization of vinyl and heterocyclic monomers. Telechelic PTHF obtained with CH3CO+/Ac2O stems from an equilibrating process and not from a transfer reaction. Telechelic polyisobutene is formed by the inifer technique of Kennedy. The use of lithium initiators with protected functional groups in butadien polymerization results in products with high 1.4‐content. The group transfer polymerisation is specially suited to prepare telechelic PMMA of narrow molecular weight distribution. The “dead end” polymerisation is a necessary condition to obtain a functionality of two by radical polymerization. The synthesis of telechelic hard segments of the PPO and PPS type is described.
Telechele des methylpropens durch kationische polymerisation
Authors: Freyer Christian V. , Mühlbauer Hans‐Peter , Nuyken Oskar 
Published: April 2003

AbstractAromatic and aliphatic hydrocarbons containing isopropyl chloride end groups in combination with boron trichloride are effective initiator systems for the cationic polymerization of methyl propene. The mathematical modelling of the proposed reaction mechanism leads to rate constants for initiation, propagation and termination which allows a good fit with experimental results. Recycling experiments have clearly shown that it is possible to reuse the coinitiator boron trichloride and the solvent dichloromethane without effecting the quality of the products.
Amphiphile polymere mit blockstruktur herstellung über makromonomere und eigenschaften
Authors: Albrecht Klaus , Wunderlich Winfried 
Published: April 2003

AbstractThe radical polymerization of methylmethacrylate (MMA) in the presence of a hydroxyl‐functional chain transfer agent (2‐mercaptoethanol) followed by reaction with 2‐isocyanatoethylmethacrylate (IEM) yielded macromonomers with molecular weights in the range of 6,5 · 103 to 23,2 · 103. Homopolymerization of the latter gave highly compact molecules which showed a solution behaviour like linear PMMA of MW = 55 000 but having a real molecular weight of 1,02 · 106. Copolymerization with methacrylic acid delivered comb‐like amphiphilic graftcopolymers with a yield of 89 %.
Alternierende copolymerisation mit lewissäuren. Copolymerisation von p‐chlorstyrol und n‐butylmethacrylat mit ethylaluminiumsesquichlorid
Authors: Braun D. , Manger E. 
Published: April 2003

AbstractNach einem Überblick über die alternierende Copolymerisation mit Lewissäuren wird die Copolymerisation von p‐Chlorstyrol und n‐Butylmethacrylat mit Ethylaluminiumsesquichlorid in Toluol untersucht (Copolymerisationsdiagramm, Zusammensetzung der Copolymeren als Funktion des Umsatzes und der Polymerisationstemperatur, Abhängigkeit der Grenzviskositäten von der Polymerisationszeit, Zeit‐Umsatz‐Diagramm). Das 1H‐NMR‐Spektrum eines annähernd äquimolaren Copolymeren bestätigt die alternierende Struktur und schließt die Möglichkeit einer Mischung aus äquimolaren Co‐ und Homopolymeren aus.
Stereoselektive polymerisation von olefinen mit homogenen, chiralen ziegler‐natta‐katalysatoren
Authors: Kaminsky Walter 
Published: April 2003

AbstractPerforming polymerizations of propylene with the stereorigid chiral ethylene(bisindenyl)zirconiumdichloride or the corresponding tetrahydroindenyl compound as transition metal components in combination with methylaluminoxane yields lightly isotactic polypropylene. Polymerization activity reaches values of more than 40 metric tonnes polypropylene per mol zirconium and hour. Polymers produced in this way display characteristical features. The mean molecular weight distribution Mw/Mn lies between 1.9 and 3 which is rather narrow. The toluene soluble(atactic) amount is less than 0.2 weight% and the 13C‐nmr spectroseopically determined isotactic sequence lengths are between 60 and 120 propene units.Polymerizations may also be run in a bubble column. In a similar manner long chain α‐olefines, such as 1‐butene, isobutene and 4‐methylpentene can be polymerized with the help of these chiral catalysts into isotactic crystalline macromolecules.
Hydrierter nitrilkautschuk ein werkstoff mit neuen eigenschaften
Authors: Obrecht Werner , Buding Hartmuth , Eisele Ulrich , Szentivanyi Zsolt , Thörmer Joachim 
Published: April 2003

AbstractDurch selektive Hydrierung der Doppelbindungen von Nitrilkautschuk (NBR) erhält man Produkte, die formal aus Ethen, 1‐Buten und Acrylnitril aufgebaut sind. Chemische und physikalische Unterschiede zwischen dem Ausgangs‐ und Endprodukt werden durch die spezifischen Eigenschaften von 1,4‐verknüpften Butadien‐ und den daraus abgeleiteten Ethensequenzen erklärt. Im Gegensatz zu Butadiensequenzen sind Ethensequenzen chemisch beständiger und können kristallisieren. Dies wird durch thermische und mechanisch‐dynamische Untersuchungen sowie die Bestimmung der Zugfestigkeit am Rohkautschuk und am rußgefüllten Vulkanisat gezeigt.
Conducting organic materials: Present status and scope
Authors: Wegner Gerhard 
Published: April 2003

AbstractElectrically conducting polymers derived from linear chain insulating macromolecules are best described as ion‐radical salts of the backbone‐units. They are obtained from the parent polymer by oxidation or reduction; in some cases the conducting polymer is obtained by simultaneous polymerization and oxidation from the corresponding polymer directly. The so called electropolymerization of pyrrole is an example for the latter case. The stability and other properties of the conducting polymers as they are related to possible applications can be understood based on the structural informations on these salts of rather high reactivity with regard to redox‐reactions.
Kristalline und flüssigkristalline copolyester substituierter und unsubstituierter 4‐hydroxybenzoesären
Authors: Kricheldorf Hans R. , Conradi Arndt , Schwarz Gert 
Published: April 2003

AbstractThree synthetic strategies were explored to lower the melting point of poly(4‐hydroxybenzoate) below 400°C. Binary copolyesters of 4‐hydroxybenzoic acid and 3‐substituted 4‐hydroxybenzoic acid were highly crystalline, regardless of composition, and did not melt below 400°C. In contrast ternary and quartenary copolyesters containing 3‐bromo‐4‐hydroxybenzoic acid may possess melting points below 360°C. Binary copolyesters of 4‐mercaptobenzoic acid and 3‐substituted 4‐hydroxybenzoic acids melt in the range of 360–400°C. Random copolyesters of 3‐(4‐hydrophenyl) propionic acid and 4‐hydroxybenzoic acid are mainly amorphous with glass‐transition temperatures between 50 and 15°C. They contain liquid‐crystalline domains, which in the case of the 1:1 copolyester are stable over a range of ca. 400°C. The heat‐distortion temperatures are low (60–80°C) due to the predominant influence of the amorphous matrix.
Nichtlineare optik. Grundlagen und eigenschaften organischer materialien
Authors: Schwoerer Markus 
Published: April 2003

AbstractIn der Optik von Huygens (1629–1695), Newton (1643–1727) und Fresnel (1788–1827)1 sind die optischen Eigenschaften der Materie unabhäangig von der Intensität des Lichts. In der nichtlinearen Optik werden die optischen Eigenschaften der Materie durch das Licht selbst dergestalt verändert, daß nach dem Abschalten des Lichts keine physikalischen oder chemischen Veränderungen in der Materie übrigbleiben. Insbesondere kann die Brechzahl in durch die Intensität I des Lichts verändert werden. Ebenso wichtig ist die Abhängigkeit der Polarisierbarkeit \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \alpha \limits_ \approx $\end{document}
von der elektrischen Feldstärke \documentclass{article}\pagestyle{empty}\begin{document}$ \overrightarrow {\rm E} $\end{document}
der Lichtwelle, sodaß das induzierte Dipolmoment \documentclass{article}\pagestyle{empty}\begin{document}$ \overrightarrow {\rm p} $\end{document}
und‐in nichtzentrosymmetrischen Körpern‐auch die Polarisation \documentclass{article}\pagestyle{empty}\begin{document}$ \overrightarrow {\rm P} $\end{document}
nicht mehr proportional zu \documentclass{article}\pagestyle{empty}\begin{document}$ \overrightarrow {\rm E} $\end{document}
sind. Damit können zahlreiche Phänomene erzeugt werden, die sowohl in ihren Grundlagen, als auch im ihere Anwendung faszinierend sind. Dazu gehören die Frequenzverdopplung, die optische Bistabilität und die Phasenkojugation. Mit Hilfe der optischen Bistabilität kann ein optisches Anologon zum Transistor‐ein Transphasor‐hergestellt werden, der Licht mit Licht ohne Umwege über elektrischen Strom schaltet. Mit Hilfe der Phasenkonjugation können vor allem verzerrungsfreie Bildübertragungen‐auch im Mikrometer‐Maßstab‐erreicht werden.
Polymers for audio and video equipment
Authors: Gossink R. G. 
Published: April 2003

AbstractPolymers find widespread use in present‐day audio and video equipment. Their applications can be divided into: (i) polymers used for the outside of the equipment, (ii) polymers used for mounting, encapsulation or passivation of electronic devices, (iii) polymers for other stationary or moving parts, (iv) polymers used for audio and video data storage, and (v) photosensitive polymers that play a temporary role in the structuring of fine details.In this paper, attention is focussed on transparent polymers (“optical plastics”) that are employed in projection television (PTV) and optical disc systems. First, the principles of these systems and the polymer properties they require are summarized, after which the polymers and technologies used in these applications are described. These polymers can be divided into two categories: (i) UV‐curable coatings on a substrate of a different nature, and (ii) transparent thermoplastics and thermosets.Finally, some shortcomings of the currently available materials are mentioned.
Polymere in der drucktechnik
Authors: Vollmann Hansjörg , Fraß Werner , Mohr Dieter 
Published: April 2003

AbstractThree main processes are used in the printing industry: Letterpress, Lithography and Gravure printing.In the early fifties polymer coatings have been introduced in lithographic printing plates formulations. Later, similar systems have proved to be suitable for letterpress, and very recently for gravure printing layers, too.Most polymer formulations used in printing techniques generally have the following features in common:• They are light sensitive• They are coated on to a flat substrate• After imagewise exposure the more soluble areas of the coatings are removed in a development step.The requirements for the polymers used in printing layers are as different as the characteristics of each individual printing process.• The importance of the specific optical properties of the polymers is demonstrated discussing some negative acting light sensitive systems, amongst them the photopolymerisation of monomers.
Kinetik der VC‐polymerisation: Ein Modellvergleich, I. Modellselektion
Authors: Weickert Günter , Henschel Gerd , WeißEnborn Klaus‐Dieter 
Published: April 2003

AbstractIn der Vergangenheit wurde eine Vielzahl kinetischer Modelle zur quantitativen Beschreibung der Polymerisation von Vinylchlorid (VC) entwickelt, die dem Praktiker die Auswahl eines geeigneten Modells erschweren. Ein Vergleich der bisher in der Fachliteratur entwickelten Modellvorstellungen anhand einer großen Anzahl experimenteller Messungen, die unter Variation der Einflußgrößen Reaktionstemperatur, Initiatorart und ‐konzentration sowie der Dispergatorart und ‐konzentration (bei Suspensionspolymerisationen) erhalten wurde, erlaubt nicht nur die Beurteilung der Modellqualität, sondern führt auch zu einem praktikablen „optimalen”︁ Modell, dessen Vorteile an Beispielen nachgewiesen werden können.
Kinetik der VC‐polymerisation: Ein Modellvergleich, II. Anwendungsbeispiele
Authors: Weickert Günter , Henschel Gerd , Weißenborn Klaus‐Dieter 
Published: April 2003

AbstractDurch Vergleich der bisher in der Fachliteratur entwickelten Modellvorstellungen zur Beschreibung der Polymerisationskinetik von Vinylchlorid (VC) bis zu hohen Monomerumsätzen wurde im Teil I dieser Arbeit1 ein Modell selektiert, das sich gut für die Auswertung experimenteller Daten aus Laboruntersuchungen sowie für die Beschreibung der Reaktionskinetik im Zusammenhang mit der modellhaften Beschreibung und Optimierung technischer Reaktoren eignet. In der vorliegenden Arbeit wird dies anhand einiger Beispiele nachgewiesen.
Identification of nylons by thin layer chromatography
Authors: Tsatsaroni Eforia G. , Kehayoglou Aristides H. 
Published: April 2003

AbstractThe composition of nylons by ω‐amino‐carboxylic acid monomers, dicarboxylic acids, and diamines is identified by thin layer chromatography, using their acid hydrolysates and determining the corresponding Rf values.
Interphase in polypropylene‐sepiolite composites based on dynamic mechanical analysis
Authors: Linares A. , Morales E. , Ojeda M. C. , Acosta J. L. 
Published: April 2003

AbstractThis paper describes the interphase between polypropylene and aldehyde surfacetreated sepiolite composites, following the method of Souma which determines a parameter based on dynamic measurements. The results obtained support the existence of a “soft” mesophase with good surface adhesion properties to the filler particle.
Methode zur Extraktion der niedermolekularen Anteile von PVC
Authors: Braun D. , Bezdadea E. , Dethloff M. 
Published: April 2003

AbstractEs wurde eine neue Methode zur Abtrennung der niedermolekularen Anteile aus PVC entwickelt. Sie beruht auf einer Löseextraktion mit Chloroform und anschließend mit Tetrachlorkohlenstoff. Die extrahierten niedermolekularen Anteile wurden viskosimetrisch, gelpermeationschromatographisch und spektroskopisch (IR und NMR) analysiert. Es wurde festgestellt, daß sie sehr niedermolekular sind und viel mehr strukturelle Defekte als das Gesamt‐PVC enthalten. Die thermische Stabilität ist bis zu achtmal geringer als die von PVC. Die Entfernung dieser niedermolekularen Anteile aus PVC ermöglicht eine erhebliche Herabsetzung der notwendigen Stabilisatormenge.
Behaviour of regenerated polyethylene, recovered from worn out packaging, to artificial ageing and under natural climate conditions
Authors: Stoica Stela , Sebe Mircea‐Octavian , Constantinescu Elena 
Published: April 2003

AbstractThis paper presents the efficiency of styrenated phenol and dian (bisphenol A) stabilizers in high density polyethylene regenerated from worn out packaging samples, by following up the regenerates' behaviour under artificial ageing as well as in natural climate conditions.The efficiency of the stabilizers was assessed by following up the characteristic physical‐mechanical modifications and the formation of carbonyl groups in the stabilized, regenerated polyethylene samples, as compared with the primary polyethylene and the unstabilized regenerated samples.
Pervaporation of water‐n‐propanol mixtures through membranes composed of poly(N‐vinylpyrrolidone)‐poly(methacrylic acid) complexes
Authors: Nieuwenhuis J. , Tan Y. Y. , van Ekenstein G. O. R. Alberda 
Published: April 2003

AbstractMembranes composed of poly(vinylpyrrolidone)‐poly(methacrylic acid) (PVP‐PMAA) complexes appear to be suitable for pervaporation of water‐n‐propanol mixtures. The membranes are selective to water. The separation factor α increases with increasing content of propanol, wPrOH, and reaches a maximum value for wPrOH at about 0.8 in the case of PVP‐rich membranes, and close to wPrOH = 1 for PMAA‐rich membranes. All membranes exhibited maximum swelling at wPrOH of ca. 0.4.At constant wPrOH of 0.8 the value of α changes in a complicated manner with the composition of the membrane. Under this condition of constant wPrOH, α runs parallel with the swelling degree. A tentative explanation is proposed for results pertaining to membranes containing not too high excesses of PVP or PMAA.
Synthesis and characterization of some 2,4′‐dibenzyldiisocyanate ionic polymers. II. Cationic polyurethances using N,N′‐bis‐(β‐hydroxyethyl)‐piperazine
Authors: Buruianǎ Tinca , Besltiuc I. , Caraculacu A. 
Published: April 2003

AbstractCationic polyurethanes containing piperazine rings on the macromolecular chain were synthesized. The polymers form flexible and transparent films. The behaviour of diluted solutions in solvents of different dielectrical constants was studied.
The effect of various pigments on the rheological behaviour and morphology of polypropylene
Authors: Pei‐Ren Li 
Published: April 2003

AbstractIn this paper the characteristics of polypropylene (PP) containing pigments are systematically studied. The results show that the flow properties of PP melt, morphological structures, and drawing behaviour of the fibres are obviously affected by the presence of certain pigments dispersed in the PP matrix. The effects of various pigments added in PP display great difference. The flow resistance of PP increases with the addition of phthalocyanine blue, carbon black, and titanium dioxide, but decreases with the presence of BR red and GL orange. The extrudate swell effects of PP melt are intensified by adding these pigments. The yield stress of filaments with rod structure is 80–125% lower than that of filaments with spherulitic structure.
Propriétés de la Surface d'un Film de Polyéthylène Modifiée par Greffage d'un Oligomère Acrylique
Authors: Lavielle Lisette , Balard Henri 
Published: April 2003

AbstractLe greffage d'un dérivé acrylique liquide (méthylène‐2 pentanedïoate‐1,5 de diéthyle) est effectué en présence de peroxyde de benzoyle à la surface d'un film de polyéthylène (HD). Les propriétés de mouillabilité de la surface sont examinées en relation avec les propriétés d'adhésion vis à vis de l'aluminium, et comparées avec celles d'un film de polyéthylène greffé dans la masse à l'acide acrylique. La mobilité des chaǐnes greffées à la surface pourrait ětre à l'origine des différences de comportement observées.
Thermal degradation studies of cellulose phosphates and cellulose thiophosphates
Authors: Kaur Baljinder , Gur Ishwar S. , Bhatnagar Hari L. 
Published: April 2003

AbstractThe thermal degradation of cellulose, cellulose phosphates, and cellulose thiophosphates was studied by differential thermal analysis, dynamic thermogravimetry, and derivative thermogravimetry from ambient temperature up to 750°C. Various thermodynamic parameters for different stages of thermal degradation of cellulose and its derivatives have been obtained following the methods of Broido, and Freeman and Carroll. Infrared spectra of thermally degraded samples were obtained. The data were analyzed in an effort to obtain more information concerning the flame‐retardant mechanisms of cellulose phosphates and cellulose thiophosphates. Lower values of decomposition temperatures and activation energies of decomposition and higher char yields of cellulose phosphates as compared to cellulose lead to the conclusion that cellulose phosphorus esters are good flame retardants, and this property is retained even when these esters were subjected to ion exchange by Na+ and K+ ions. However, with the introduction of sulphur atoms, there was some decrease in this property.
Die polymerisation von lactamen, 86. Verzweigung der autopolymerisationsprodukte von 8‐octanlactam
Authors: Prokopová Irena , Tuzar Zdeněk , Kondelíková Jaroslava , Králíček Jaroslav 
Published: April 2003

AbstractDurch das Studium der Lösungseigenschaften des unter Bedingungen der Autopolymerisation im Temperaturbereich 240–260°C hergestellten Poly(8‐octanlactam) wurde die angenommene Verzweigung der Polymerketten bestätigt. Nach der Hydrazinolyse der Polymeren wurden in den Polymerketten Amidinstrukturen identifiziert, die jedoch für das Entstehen der Verzweigungszentren nicht im vollen Ausmaß verantwortlich sein können.
Synthesis and polymerization of new vinyl derivatives of thymine
Authors: Akashi Mitsuru , Tanaka Yasuo , Iwasaki Hiroaki , Miyauchi Noriyuki 
Published: April 2003

AbstractN‐acryloyl and N‐methacryloyl derivatives of thymine were prepared by one‐step reaction of silylated thymine with acryloyl chloride and methacryloyl chloride, respectively, in good yields. These vinyl monomers containing thymines were polymerized and copolymerized with water soluble vinyl monomers such as acrylamide and vinylpyrrolidone by free‐radical polymerization. Complex formation between copolymers and RNA in aqueous solution was studied by means of UV spectroscopy.
Radiation initiated grafting on fluoro polymers III. Grafting of N‐vinylpyrrolidone in aqueous solution on poly(vinylidene fluoride) films by accelerated electrons
Authors: Niemöller Axel , Ellinghorst Guido 
Published: April 2003

AbstractThe radiation induced grafting of N‐vinylpyrrolidone in aqueous solution onto poly(vinylidene fluoride) (PVF2) films by preirradiation technique using 160 keV electrons has been investigated. Among the grafting parameters, the most important are storage time after irradiation, grafting time, grafting temperature, and absorbed dose. Trapped radicals in PVF2 are very stable; peroxy radicals generated by storage of irradiated samples in air can initiate grafting, too. The grafting of PVF2 proceeds slowly from the film surface to the inner part, ceasing when the middle of the film is reached from both sides. The penetration of the grafting front has been observed by “Differential‐Interference‐Contrast” (DIC)‐microscopy. At constant other parameters, the penetration depth depends on the grafting time and can be correlated with the time conversion curves. For the discussion of the grafting reaction a simple kinetic model has been developed. A very high activation energy of diffusion of ∼ 80 kJ mol−1 has been estimated both by sorption measurements and by application of the kinetic model with regard to the activation energies of grafting rate and saturation grafting yield (SGY). From the SGY‐dose relationship the ratio of the rate constants kpkt−1 has been calculated. As for other grafting systems this ratio has about the 105‐fold value in relation to homopolymerization of the same monomer. This indicates the restrained mobility of propagating macroradicals in the highly viscous grafting medium leading particularly to a lower kt in comparison with homopolymerization.