bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aromatic diamines as multifunctional ingredients in halogenated butyl rubber
Authors: Ivan G. , Tavaru E. , Giurginca M. 
Published: April 2003

AbstractThe crosslinking of halogenated butyl rubber by aromatic diamines is investigated. The crosslinking process was realized by thermal activation or in conditions of mechanical processing. The main investigated influencing factors were nature of the diamine, temperature, nature of halogen, presence of metallic oxides. The formation of bound antioxidant was made obvious by the determination of the extractable amount of antioxidant as well as by following the ageing behaviour of the elastomer.
Copolymerization of multimethacrylate with vinyl monomers
Authors: Jantas R. 
Published: April 2003

AbstractThe free radical copolymerization of multimethacrylate with styrene and acrylonitrile in dilute dimethylformamide solutions has been investigated. The effects of the copolymerization conditions on the content of unreacted double bonds, molecular weight, and composition of the copolymers were determined. Based on IR and 1H‐NMR spectra the structures of the copolymers were confirmed. The examination of copolymerization in the presence of AIBN labeled with 14C allowed to determine the number of branching points in a macromolecule. The results show that the copolymerization process results in copolymers composed partly of ladder‐type blocks and blocks of vinyl monomer units. The thermal properties of the copolymers were determined.
Characterization of diol modified epoxy resins by means of thermomechanical analysis and measurements of compressive modulus
Authors: Tänzer W. , Häusler K.‐G. , Kunze A. 
Published: April 2003

AbstractGlass transition temperatures Tg of diol modified epoxy resin networks were determined using thermomechanical analysis. These temperatures depend on concentration and chain length of the diol and furthermore on the type of the accelerator. Measurements of uniaxial compressive modulus gave a similar dependence for the shear modulus G and the network density.
A critical analysis on different criteria of the mechanical stability of polymeric membranes operating in the pressure‐driven processes
Authors: Islam M. A. , Dimov A. 
Published: April 2003

AbstractDifferent criteria for the evaluation of the mechanical stability of polymeric membranes have been discussed. It has been illustrated that the hysteresis curves are the measure only for the plastic deformation of the membrane in a given cycle. Flux‐decline rate accounts for the viscoelastic and plastic deformation of the membrane. For the appropriate characterization of the mechanical stability all types of deformation should be taken into account. In the present paper a criterion is proposed which accounts for the elastic, viscoelastic, as well as plastic deformations of the membrane.
Optical absorption in gamma irradiated poly(vinyl alcohol)‐CoCl2 composites
Authors: Sharaf F. , Khaled M. A. , Abdel‐Rahman A. A. , Basha A. F. 
Published: April 2003

AbstractOptical absorption measurements were performed on cast thin films of poly(vinyl alcohol) and its composites with cobalt chloride before and after gamma irradiation. Identification of the structure and assignments of energy bands have been derived in terms of ligand field theory. A mechanism based on the equilibrium between six‐coordinated and four‐coordinated symmetry is proposed to account for the obtained spectra. The symmetry is found to be altered with both cobalt concentration and gamma irradiation dose.
Bildungsweise, Strukture und Anwendungsmöglichkeiten von Komplexen zwischen Polyelektrolyten und ionischen Farbstoffen (Literaturübersicht) Teil II: Komplexe zwischen anionischen Polymeren und kationischen Farbstoffen
Authors: Dawydoff W. , Linow K.‐J. , Philipp B. 
Published: April 2003

AbstractBildungsweise und Struktur von Komplexen zwischen anionischen Polymeren und kationischen Farbstoffen werden beschrieben, wobei sowohl synthetische Polyelektrolyte als auch saure Polysaccharide und Peptide betrachtet werden und als Farbstoffkomponente Acridinorange und Methylenblau im Mittelpunkt stehen. Auf einige praktische Anwendungsmöglichkeiten von Polyelektrolyt‐Farbstoff‐Komplexen sowie auf die Bindungsarten zwischen den Komplexbestandteilen wird eingegangen.
The copolymerization reactions of N‐(2‐methyl‐5‐dimethylaminophenyl)maleimide
Authors: Lokaj J. , Bílá J. 
Published: April 2003

AbstractThe radical copolymerization of N‐(2‐methyl‐5‐dimethylaminophenyl)maleimide (I) with styrene (S), methyl methacrylate (MMA), 2‐dimethylaminoethyl methacrylate (DAMA), acrylonitrile (AN), methacrylic acid (MA), and isoprene (IP) was investigated. The reactivity ratios of pairs of monomers I ‐ S, I ‐ MMA were determined, and the Alfrey‐Price constants e, Q of the imide I were calculated. Along with the copolymerization of I with IP, the Diels‐Alder addition proceeding in parallel was also followed.
Biodegradable polymers. 6th comm. Polymerization of ϵ‐caprolactone
Authors: Rafler G. , Dahlmann J. 
Published: April 2003

AbstractThe ring‐opening polymerization of ϵ‐caprolactone was investigated in dependence on the most important reaction parameters. It was found that the monomer conversion is above all determined by polymerization temperature just as type and concentration of initiator. High yields of polymer can be obtained by initiation with tin(II) carboxylates, tin(II, IV) halogenides and titanium alkylates. The molecular weight of the polymer depends in a complex manner on the reaction conditions because the primary ring‐opening reaction is accompanied by consecutive reactions. The values of molecular weight pass through a maximum.
Topologische Struktur und Lösungseigenschaften von verzweigten diallylesterpolymeren
Authors: Pavlova O. V. , Kireeva S. M. , Sivergin Ju. M. 
Published: April 2003

AbstractDie topologische Struktur und die Eigenschaften verdünnter Lösungen von verzweigten Polymeren auf Basis von Diallylestern der Sebazin‐und Isophthalsäure wurden in einem weiten Bereich der Molekülmassen untersucht. Die untersuchten Systeme stellen stark verzweigte Polymere dar, die kammartige und statistische Kurzkettenverzweigungen sowie eine große Anzahl intramolekularer Cyclen enthalten. In verdünnter Benzenlösung haben die verzweigten Polymere eine untere kritische Mischungstemperatur. In einem guten Lösungsmittel weisen die polymeren Knäuel sehr niedrige Werte der Grenzviskosität auf. Diese Erscheinungen hängen mit der besonderen topologischen Struktur der untersuchten Systeme zusammen.
Löslichkeitsuntersuchungen an Copolymeren aus Styren und Maleinsäureanhydrid durch Trübungstitration
Authors: Francuskiewicz F. , Heinemann M. , Müller S. , Glöckner G. 
Published: April 2003

AbstractMittels Trübungstitrationen an Lösungen von Styren/Maleinsäureanhydrid‐Copolymeren wurde festgestellt, daß mit Alkoholen als Fällungsmittel bevorzugt nach der Molmasse fraktioniert werden kann, während sich Kohlenwasserstoffe besser zur Trennung nach der chemischen Zusammensetzung eignen. Methanolyse‐Reaktionen an den Anhydridbausteinen verändern die Fällbarkeit merklich.
Zum einfluß von düsenverzug und plastischer reckung auf die eigenschaften von naßgesponnenen polyoxadiazolfäden
Authors: Stark W. , Remde H. , Leonhardt R. , Strauß K.‐H. , Strubl R. 
Published: April 2003

AbstractPolyoxadiazol, ein aromatisches heterocyclisches Polymer, ist aufgrund seiner hohen thermischen Stabilität für eine Reihe von Einsatzzwecken interessant. Mit einer Laborspinnanlage wurden die Spinnbedingungen Düsenverzug und Grad der plastischen Reckung variiert und deren Einfluß auf die Materialparameter wie Bruchdehnung, Festigkeit und Modul untersucht. Zur Erreichung höherer Festigkeiten und Moduli erwiesen sich ein mittlerer Düsenverzug von 2 und ein eher niedriger plastischer Reckgrad von 1,5 bis 2 als günstig. Ebenfalls untersucht wurde die Längenzunahme der Fäden bei lastfreier Temperung. Je nach Düsenverzug und plastischem Reckgrad wurden sowohl positive als auch negative Längenänderungen gefunden, die mit der überlagerung von spontaner Dehnung und Schrumpf erklärt werden.
Polyanion‐polycation‐complex formation of charged microgels and latices with oppositely charged polyelectrolytes in solution
Authors: Kötz J. , Paulke B. , Philipp B. , Denkinger P. , Burchard W. 
Published: April 2003

AbstractEmploying cationic, covalently crosslinked polyallylamine‐based highly swollen microgels and anionic latices obtained by copolymerization of methacrylic acid and epoxypropyl methacrylate, the interaction of these polymer colloids with oppositely charged linear macroions is investigated by potentiometry, conductometry and turbidimetry. The microgels behave similar to linear macroions in symplex formation, if the components are reacted in the neutralized state, while in a “free acid – free base” titration only the easily accessible sites of the microgels are primarily involved in the interaction. With the more compact polymer latices a stable dispersion is formed, while with the microgels flocculation occurs. The results are discussed with regard to the influence of physical structure of the polymer colloids on stoichiometry and state of dispersion of the symplexes formed.
Indications of the excluded volume effect in the core of a polymer colloid particle
Authors: Pekcan Ö. 
Published: April 2003

AbstractThe phosphorescence intensity of naphthalene groups labelled to the poly(methyl methacrylate) phase of a colloid particle is studied in dependence of temperature. The peculiar structure in the phosphorescence spectra around −126 °C is attributed to the theta point conditions of the colloid dispersion. The results are interpreted in terms of the excluded volume effect.
The sorption of ethyl xanthogenate on polyester fibres. II. Kinetics and thermodynamics
Authors: Espinosa‐Jiménez M. , Cano‐Suárez A. 
Published: April 2003

AbstractData on the kinetics and thermodynamics of absorption of potassium ethyl xanthogenate onto polyester fibres at different temperatures are presented. It is established that the increase in temperature of the system increases the uptake of ethyl xanthogenate ions by the fibres. Adsorption equilibria, specific rate constants, diffusion coefficients, activation energy and enthalpy of reaction were determined. From the results the conclusion can be derived that the adsorption of ethyl xanthogenate ions on the polyester fibre in the investigated temperature interval takes place with establishment of strong chemical bonds.
Dielectric investigation by time domain spectroscopy of vinyl chloride/vinylidene chloride copolymer solutions
Authors: Menge H. , Feldman Yu. D. , Polygalov E. , Fedotov V. D. , Schneider H. 
Published: April 2003

AbstractDielectric time domain spectroscopy measurements were performed on vinyl chloride/vinylidene chloride copolymers in solution over a frequency range of 1 to 104 MHz. The dielectric absorption and dispersion have been studied at temperatures from −20°C to +20°C. The data were analyzed by using the Havriliak‐Negami equation and related to the motional behaviour. The dielectric correlation function was compared with those from different motional models used in NMR experiments.
Synthesis and substituent distribution of Na‐cellulose sulphates via O‐trimethylsilyl cellulose as intermediate
Authors: Wagenknecht W. , Nehls I. , Stein A. , Klemm D. , Philipp B. 
Published: April 2003

AbstractSulphation of cellulose was performed in an homogeneous aprotic system with SO3 or CISO3H, resp., via O‐trimethylsilyl celluloses as reactive intermediates. Na‐cellulose sulphates completely soluble in water and showing small chain degradation could be obtained at DSs≥ 0.25. The DSs in the range between 0.2 and 2.5 as well as the distribution of the sulphate half‐ester groups within the AGU were regulated via the DSsi at one hand, the type and amount of sulphating agent at the other. Sulphation was performed either with the isolated and redissolved trimethylsilyl cellulose in N,N‐dimethylformamide or tetrahydrofurane, or starting with an activated cellulose suspension, by achieving silylation and subsequent sulphation in one system of reaction. Obviously, the silyl group acts as a reactive group in subsequent sulphation, and the sites previously silylated are preferentially sulphated in the subsequent step of reaction, and the DSs is limited by the degree of silylation (DSsi) previously obtained. The homogeneous sulphation of trimethysilyl cellulose indicates a reactivity of silyl ether groups in the order of C‐6 > C‐2 ≫ C‐3.
Synthesis of nanoparticles for brain cell labelling in vivo
Authors: Paulke B.‐R. , Härtig W. , Brückner G. 
Published: April 2003

AbstractDifferent types of latices were synthesized by emulsion copolymerization that differ in particle size, polymer hydrophilicity and surface coverage with functional groups. All of these particles were equipped with intensive fluorescence by inclusion polymerization, covalent bonding during particle formation and growth or surface modification of pre‐fabricated latices, respectively. Concentrated particle suspensions were injected into the brain tissue of mice. The filling of glial cells by phagocytosis and the retrograde labelling of neurons with two kinds of beads could be shown in brain sections.
Pure and modified polycyanurates ‐ polymers with great future as adhesives, casting resins, and binders for laminates
Authors: Bauer M. 
Published: April 2003

AbstractPure and modified polycyanurates are known for about 20 years. Up to now an important number of different special products was developed. Composites which base on polycyanurate resins show a high thermostability, stability against humidity and chemicals, and excellent electrical insulating properties. The resins are used as adhesives, binders for laminates, casting resins, and for other applications.
Thermodynamics of blends of poly(vinyl methyl ether) and polystyrene
Authors: Troeger J. , Kammer H. W. 
Published: April 2003

AbstractLight scattering is employed to determine cloud point curves of polystyrene (PS)/poly(vinyl methyl ether) blends over a large range of PS molecular weights. All blends investigated display lower critical solution temperature (LCST) behaviour. The LCST shifts to lower temperatures and smaller PS contents with ascending disparity of the constituent's molecular masses. Thermodynamics of the blends has been rationalized in terms of an equation‐of‐state theory. Relevant parameters can be calculated. Both enthalpy of mixing and excess volume turn out to be negative.
Dielectric relaxation of amorphous random copolymers of poly(ethylene terephthalate) and poly(ethylene‐2,6‐naphthalene dicarboxylate)
Authors: Ezquerra T. A. , Baltà‐Calleja F. J. , Zachmann H. G. 
Published: April 2003

AbstractThe dielectric constant and dielectric loss values have been determined in the 103‐106 Hz frequency range for amorphous random copolymers of poly(ethylene terephthalate) (PET) and poly(ethylene‐2,6‐naphthalene dicarboxylate) (PEN). The dielectric behaviour has been interpreted in terms of the Havriliak‐Negami formulation. On this basis the variation of the dielectric properties with temperature has been qualitatively related mainly to two processes: The α process which is associated to the glass transition of the polymer and depends on the molar ratio of PET and PEN. The β process which is assigned to a local motion of the ‐COO groups attached to the aromatic rings. The existence of a β* process in between the α and the β processes has been observed in PEN at low frequencies. The relaxation time spectrum has been discussed in terms of molecular structure alterations. Finally, the temperature variation of the relaxation time is analyzed in the light of various predictions.
Rotational dynamics of substituted phthalocyaninatopolysiloxanes as measured by 2D solid‐state NMR spectroscopy
Authors: Schwiegk S. , Werth M. , Leisen J. , Wegner G. , Spiess H. W. 
Published: April 2003

AbstractThe rotational dynamic behaviour of a polymer of the hairy rod type has been investigated in the solid state. Octa‐(alkoxy)‐phthalocyaninatopolysiloxanes have been synthesized selectively deuterated at the aromatic core positions for this study. They form a hexagonal columnar structure without any phase change in the temperature range from 170 to 470 K. Thermally activated uniaxial rotation involving the phthalocyanato moiety around the long axis of the polymer is detected by solid‐echo 2H‐NMR spectroscopy. Two‐dimensional NMR spectroscopy shows that the motional process involves 90° jumps with considerable broadening of the reorientation potential, reflecting the four‐fold symmetry of the repeat unit. This indicates that the siliconphthalocyanine moieties can rotate around their covalent Si‐O bond within a single macromolecule, rather than the molecules as a whole around their columnar axes.
Tracer‐diffusion in quenched lamellar phases
Authors: Fredrickson G. H. 
Published: April 2003

AbstractA theory is presented to describe the tracer‐diffusion properties of surfactant molecules embedded in quenched, disordered lamellar phases, such as those encountered in concentrated solutions and melts of block copolymers. We demonstrate that for weak anisotropy of the local diffusion tensor Dij, the average diffusion coefficient of an isotropically disordered sample is slightly larger than (1/3)∑iDii and is independent of the geometrical and statistical details of the quenched pattern. For large anisotropy of Dij, transport of a tracer molecule will in general become dependent on the population and type of topological defects that characterize the quenched sample and thus on its preparation and history. In such instances, sub‐diffusive transport can be achieved.
Investigation of stress distributions in filled polysiloxane by NMR imaging
Authors: Blümler P. , Blümich B. 
Published: April 2003

AbstractNMR imaging is applied to industrial poly(dimethylsiloxane). Samples were investigated in the strained and unstrained state with and without a cut, and compared with two model compounds. Inhomogeneous filler distributions cause variations in the magnetic susceptibility and lead to contrast in gradient‐echo images.T2‐parameter images revealed distributions in segmental mobility associated with the filler inhomogeneities as well as with the cut. The images were recalibrated to give strain and stress images by use of integral stress andT2values determined for macroscopic uniaxial strain. The effects of filler inhomogeneities appear larger in the NMR images than in polarization micrographs because of magnification by magnetic field distortions from susceptibility differences in gradient‐echo images, and because changes in segmental mobility of surrounding polymer chains are detected rather than the filler itself. The methods can also be applied to 3D imaging of nontransparent rubbers.
Synthesis, electrical conductivity and electroluminescence of poly(p‐phenylene vinylene) prepared by the precursor route
Authors: Gmeiner J. , Karg S. , Meier M. , Rieß W. , Strohriegl P. , Schwoerer M. 
Published: April 2003

AbstractWe present a detailed experimental procedure for the synthesis of poly(p‐phenylene vinylene) by the precursor route. Special emphasis is given to the conditions of the thermal elimination reaction that leads from the processable precursor polymer 4 to PPV. We found that a temperature of 320°C is necessary to remove sulphur and chlorine containing defect structures which are probably formed by nucleophilic substitutions during thermal elimination. PPV prepared by our procedure contains 0.12% of chlorine and 0.15% of sulphur. With this material we are able to prepare large area light emitting diodes (LED) which work at driving voltages as low as 2 Volts in an ITO/PPV/Al configuration. The low threshold results in an improved device performance: So a LED continuously driven with a current density of 20 mA/cm2 emits light for one week at ambient conditions and for more than four weeks if operated in a glove box at room temperature.
The formation of polymer‐solvent complexes of polyacrylonitrile from organic solvents containing carbonyl groups
Authors: Bashir Z. , Church S. P. , Price D. M. 
Published: April 2003

AbstractThe crystallisation behaviour on cooling of concentrated solutions of polyacrylonitrile (PAN) in two organic solvents, gamma butyrolactone (gBL) and ethylene carbonate (EC), was investigated. gBL is a liquid but EC is a crystalline solid at 20°C. Wide angle X‐ray diffraction studies showed that the peaks from the solvent‐containing gel films were different from those in the dry PAN powder. Polarised‐infrared spectroscopy measurements conducted on uniaxially‐drawn gel films indicated not only preferential orientation of the nitriles perpendicular to the draw direction but also orientation of the residual solvent in such a way as to suggest pairing of the gBL or EC molecule with the nitriles on the chains. It is suggested that the X‐ray diffractograms of the gels may be due to the formation of polymer‐solvent complexes during crystallisation of PAN from solvents with carbonyl groups. Differential scanning calorimetry showed gel‐melting endotherms on heating and crystallisation exotherms on cooling.
Atomistic details of disordering processes in superheated polymethylene crystals
Authors: Liang G. L. , Noid D. W. , Sumpter B. G. , Wunderlich B. 
Published: April 2003

AbstractAtomistic details of disordering in superheated polymethylene crystals have been studied using molecular dynamics simulations. Superheating causes a quick development of large‐scale disorder throughout the crystal, including reorientation, translation, and the destruction of crystal symmetry, followed ultimately by surface melting. Crystallization‐centers with hexagonal packing are found in the superheated, unconstrained crystals. On cooling during the simulation, a recrystallization process competes with the disordering resulting in a reorientation of the molecular chains and reorganization of the crystal.“The submitted manuscript has been authored by a contractor of the U.S. Government under contract No. DE‐AC05‐84OR‐21400. Accordingly, the U.S. Government retains a nonexclusive, royalty‐free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.”
Correlation between structure and electrical conductivity of soluble polyphenylenes
Authors: Simitzis J. , Tzevelekis D. , Stamboulis A. , Hinrichsen G. 
Published: April 2003

AbstractPolyphenylenes were prepared by using biphenyl‐AlCl3‐CuCl2 according to cationic oxidative polymerization. The chlorobenzene soluble fraction was doped with 10% (w/v) solution of FeCl3 in acetonitrile. The alternating electrical conductivity, X‐ray diffractograms and the FTIR‐spectra of both undoped and doped polyphenylenes were measured. The proportion of the components used for the preparation of polyphenylenes strongly influences their structure as well as their conductive properties. The undoped polyphenylenes were found to be insulators, but most of them became semiconductors after doping. The increase of the alternating electrical conductivity σ' (resulting from the real part of the admittance‐vector) of the doped polyphenylenes has been explained considering the factors that influence the polyphenylenes structure: the high ratio of para/meta, the presence of both amorphous and crystalline regions, and the presence of polynuclear structures. On the other hand, the presence of aliphatic structures interrupts the conjugation system, leading to lower σ' values.