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  • Polymer and Materials Science  (108)
  • Inorganic Chemistry  (81)
  • 1990-1994  (189)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1061-1067 
    ISSN: 0009-2940
    Keywords: Buckminsterfullerenes ; Organodihydrofullerenes ; Fullerene derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Controlled two-step nucleophilic hydroalkylations, hydroar-ylations as well as hydrostannylations of fullerene-60 (1) and fullerene-70 (2) lead to defined organodihydrofullerenes C60HR and C70HR. NMR investigations show that only one isomer of each organodihydrofullerene with Cs symmetry is formed. In all cases the addition takes place at a double bond separating two six-membered rings of the fullerene core. In this way a variety of organodihydrofullerenes also carrying functional groups have been synthesized.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2423-2429 
    ISSN: 0009-2940
    Keywords: Triazenes, aryl ; Radical cations ; Cyclic voltammetry ; ESR spectroscopy ; UV-Vis spectroelectrochemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,3-Dimethyl-1-(4-R-phenyl)- [R = (CH3)2N, C2H5O, CH3O, CH3; 3] and 3-Methyl-1-(4-R1-phenyl)-3-(4-R2-phenyl)triazenes [R1 = (CH3)2N, CH3O, NO2, R2 = CH3O, H, 4] are oxidized electrochemically and chemically to their one-electron oxidation products. Cyclic voltammograms of the triazenes are discussed, and ESR as well as UV/Vis spectra of the radical cations are presented. The stability of the triazene radical cations generated depends on the substituents on the aryl rings. 4-R-Benzenediazonium ions are identified as one of the decay products of the radical cations by means of cyclic voltammetry and UV/Vis spectroelectrochemistry.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 5 (1994), S. 105-109 
    ISSN: 1042-7147
    Keywords: Oligomer ; Arylenevinylene ; Polystyrene ; Polycarbonate ; Blends ; Light-emitting diodes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A bisstyrenebenzene with improved solubility can be obtained by a lateral phenyl substituent on the phenylene ring. The phenyl substituted bisstyrenebenzene (PBSB) was synthesized by Pd-catalyzed coupling of 2,5-dibromobiphenyl and styrene. PBSB exhibits blue fluorescence in solution. Blends of PBSB and polystyrene or polycarbonate are homogeneous over a wide concentration range of PBSB, based on differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results were compared with the blending behavior of unsubstituted bisstyrenebenzene.
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  • 4
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 5
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The tensio-active properties of different types of diesters can be used to synthesize two-dimensional model networks at the interface between oil and water. We have systematically studied rubber-elastic, glass-like and transient membrances which are stabilized and crosslinked by physical or chemical contacts.The adsorption process of the monomeric diesters was investigated by measuring the interfacial tension at the boundary between oil and water. The experimental results can be interpreted on the basis of the “Szyskowski”- equation which holds for monomolecular films under ideal conditions. From the measured values of the interfacial tension it is possible to determine the surface concentration. The polymerization process occurs through radical-reactions which can be initiated by UV-irradiation.We have systematically studied the kinetics of surface gelation by measuring the two-dimensional shear modulus as a function of the reaction time. The experimental results can be interpreted in the framework of simple reaction mechanisms. The quantitative analysis of the experimental data allows to evaluate many details of the photo-reaction as the free radical concentration. the number of linear chains and the rate constant of the cross-linking process.The two-dimensional sol-gel transition can easily be described in the framework of percolation theories which were proposed by Stauffer and de Gennes. According to these models, one expects to find a steep increase in the elastic modulus after passing the gel point. The two-dimensional percolation exponent, determined in our experiments, agrees very well with the calculated result of 4/3. This holds for rubber-elastic and glass-like membranes.Rubber-elastic, cross-linked films exhibit interesting features, which can be explained by simple models. The shear modulus depends upon the surface concentration of elastically effective chains. The interfacial polymerization is not restricted to flat surfaces, and the corresponding films can be used for the stabilization of different types of emulsions. Oil droplets which are surrounded by cross-linked membranes, from simple systems which exhibit interesting properties of biological cells. The microcapsules can, for instance, be used in order to simulate blood flow in living vessels. We have measured the deformation process and the aggregation behavior of these microcapsules in Couette flow under a microscope, and we have investigated the influence of the membrane elasticity on the flow behavior of these emulsions. The data, thus obtained, can be compared with the particle behavior of rigid spheres and deformable liquid drops. The rheological properties of these artificial cells are useful to get a clearer picture of the complicated flow processes which occur in biological systems.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 211 (1993), S. 141-155 
    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 after-glow Plasmapolymerisation wird als neues Verfahren zur Herstellung polymerer Schichten aus ungesättigten Monomeren vorgestellt. Als Monomeres wird ein optisch aktiver Acrylsäureester verwendet. Die Abscheidekinetik wird durch Variation von Monomerfluß, Fluß und Art des Hilfsgases (He, Ne, Ar, Kr) Abstand zwischen Plasma und Substrat, Druck und nomineller Plasmaleistung untersucht. Die erhaltenen Polymeren sind optisch aktiv und lassen sich mittels IR_Spektroskopie nicht von den in Masse polymerisierten Analoga unterscheiden. Die Polymeren sind meist vernetzt und damit unlöslich. NMR-Spektren von Löslichen Proben zeigen, daß es sich um atktische Polymere handelt. Die after-glow Plasmapolymerisation verläuft über einen radikalischen Kettenwachstumsmechanismus. Membranchichten aus den erhaltenen Polymeren sind in der Lage, Racemate zu trennen.
    Notes: After-glow plasma polymerization is described as a new method to prepare polymeric layers from unsaturated monomers. An optically active acrylic monomer is used in this investigation. The deposition rates are given as functions of plasma power, pressure, distance between plasma and deposition zone, flux and kind of auxiliary gas (He, Ne, Ar, Kr) and of monomer flux. The polymers prepared are optically active, the IR spectra comply with those of polymers synthesized in bulk. Mostly the polymers prepared by after-glow plasma polymerization are cross-linked and therefore insoluble. NMR spectra of soluble samples show that the polymers are atactic. After-glow plasma polymerization occurs by a radical chain growth mechanism. Membranes made from these polymers are able to separate racemates.
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  • 8
    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 Polykondensation aliphatischer Dicarbonsäuren wie Bernsteinsäure, Iminodiessigsäure und Ethylendiamintetraessigsäure (die als difunktionelles Monomeres reagierte) mit Diaminen wie Diethylentriamin, l, 2-Bis(3-aminopropylamino)ethan und den beiden löslichkeitsverbesserenden Polyethylenoxid-Derivaten α,ω-Bis(2-aminopropyl)polyethylenglykol800 (Jeffamine ED-900) und α,ω-Bis-(2-aminopropyl)- poly-ethylenglykol 1900 (Jeffamine ED-2001) wurden hydrophile Polyamide mit Aminooder Carboxygruppen in ihren Wiederholungseinheiten hergestellt, die zur Ankopplung physiologisch aktiver Substanzen geeignet sind. Die Reaktionen wurden in Polyphosphorsäure im optimalen Temperaturbereich von 150- 165°C durchgefuhrt. Die Produktpolymeren wurden durch Dialyse wäßriger Lösungen fraktioniert und durch Gefriertrocknung isoliert. Die Ausbeuten, die von 1% bis nahe 40% reichten, zeigen für das fluchtige Diethylentriamin unter diesen Bedingungen eine geringe Tendenz zur Polykondensation und eine mittelmanige Reaktionsneigung fur die thermolabilen Jeffamine-Reaktanden, während für das Bis(aminopropylamino)ethan eine zufriedenstellende Polykondensationsbereitschaft gefunden wurde. Die mikroanalytisch und spektroskopisch charakterisierten Polyamide verfügen über eine  -  für biomedizinische Anwendungen wichtige  -  ausreichende Wasserlöslichkeit. Die inhärenten Viskositäten in diesem Medium liegen im Bereich von 5 - 15 ml g-1. Die Nutzung dieser Polymeren zur Verankerung von Medikamenten wird Gegenstand weiterer Veröffentlichungen sein.
    Notes: Hydrophilic polyamides containing amino or carboxyl groups in the repeat units suitable for drug binding are synthesized by polycondensation of aliphatic dicarboxylic acids, including succinic acid, iminodiacetic acid, and ethylenediaminetetraacetic acid (reacting as a difunctional monomer in these polymerizations), with diamines, such as diethylenetriamine, 1,2-bis(3-aminopropylamino)ethane, and the two hydrosolubilizing poly(ethylene oxide) derivatives, α,ω-bis(2-aminopropyl)poly(ethylene glycol) 800 (Jeffamine ED-900) and α,ω-bis(2-aminopropyl)poly(ethylene glycol) 1900 (Jeffamine ED-2001). The reactions are conducted in polyphosphoric acid medium at the optimal temperature range of 150-165°C. The product polymers, fractionated by aqueous-phase dialysis in 12000-14000 molecular-mass cut-off membrane tubing, are isolated by freeze-drying. Yield data, ranging from 1% to nearly 40% for the material so fractionated, indicate low propensity for polycondensation under these conditions for the volatile diethylenetriamine monomer, and only moderately better performance for the thermally labile Jeffamines, yet satisfactory polymerization behaviour for the bis(aminopropylamino)ethane. The microanalytically and spectroscopically characterized polyamides fulfil the biomedically important requirement of solubility in water; inherent viscosities in this medium are in the approximate range of 5-15 ml · g-1. The drug-anchoring capabilities of these polymers will be the subject of forthcoming publications.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1175-1183 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The temperature dependence of hydrogen isotope exchange rates for lysozyme in 5 molal aqueous glycerol and for poly (D,L-alanine) in a range of glycerol concentrations from 0 molal to 8 molal have been determined. The activation enthalpy of base-catalyzed exchange for poly (D,L-alanine) in water is 4 kcal/mol and passes through a minimum at about 2 molal glycerol before returning to a value of 4 kcal/mol at 4 molal glycerol. Exchange rates for lysozyme have been analyzed with transition state and Kramers's theories. The activation parameters for exchange of protons in lysozyme in the presence of 5 molal glycerol show a similar qualitative behavior to those determined for exchange in the absence of glycerol [R. B. Gregory et al. (1982) Biochemistry 24, 6523-6530]. The activation enthalpies and entropies for the fast-exchanging protons show a gentle increase as H(t), the number of hydrogens remaining unexchanged, decreases. By contrast, the activation parameters for the slowest exchanging protons [H(t) 〈 20] increase dramatically as H(t) decreases. As in water, the activation parameters for exchange of the fast- and slow-exchanging protons in glycerol solution are characterized by two distinct compensation temperatures (510 ± 100 K for the fast protons and 340 ± 40K for the slow protons). These values are not significantly different from those determined for exchange in water.The activation parameters, ΔH
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Individual DNA molecules in the Mb size range were monitored by epifluorescence video microscopy during field inversion gel electrophoresis (FIGE). DNA migrating in an agarose gel gives rise to characteristic V-conformational elements and when doing so exhibits a reduced mobility. When the V-conformational elements per DNA molecule are few, the degree of retardation appears proportional to the number of V's, and since larger DNA species exhibit more V's, to DNA size. For a particular pulse frequency, the proportionality breaks down progressively as the number of V-conformational elements per DNA molecule increases. The loss of proportionality between DNA length and migration rate is being correlated with the macroscopically observed loss of electrophoretic size discrimination known as band compression. For a particular pulsing frequency and size class of DNA, the loss of size discrimination is thought to be due to the different orientations of migration, caused by the asymmetric distribution of V-conformational elements when the number of these elements is moderate. Small and very large DNA by contrast migrate with the direction of the biased field. These events, analyzed by microscopic measurement, are consistent with the known macroscopically observed double-valued mobilities in FIGE.
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