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  • 1
    Electronic Resource
    Electronic Resource
    Investigation of synthesis and light stability of polymeric azo dyes. I. Polymeric urethane-azo dyes (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 197 (1992), S. 159-173 
    Details
    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: Ausgehend von 10 unterschiedlich 4′-substituierten 4-[N,N-dihydroxyethyl]aminoazobenzolen wurden durch Umsetzung mit Hexamethylendiisocyanat polymere Azofarbstoffe (M̄n 4200-10200) synthetisiert und die Substituentenabhängigkeit der spektralen Eigenschaften, der Redoxpotentiale und des Ausbleichverhaltens mit entsprechenden monomeren und dimeren Modellverbindungen verglichen. Die Ausbleichung erfolgt durch einen photooxidativen Prozeß. In der Reihenfolge monomerer 〉 dimerer 〉 polymerer Azofarbstoff sinkt die Lichtstabilität durch die Verringerung thermischer Desaktivierungsprozesse sowie durch einen möglichen intramolekularen Energietransfer.
    Notes: Starting from 10 different 4′-substituted 4-[N,N-dihydroxyethyl]aminoazobenzenes, polymeric urethane-azo dyes (M̄n 42000-10200) were prepared by reacting those with hexamethylene diisocyanate. The dependence of spectral properties, redox potentials and photofading behaviour on the kind of substitutents was determined and then compared with corresponding monomer and dimer model compounds. Photofading is caused by a photooxidative process. In the sequence of monomeric 〉 dimeric 〉 polymeric azo dyes, light stability decreases due to a diminution in thermal disactivation processes and in a possible intramolecular energy transfer.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.051970114
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  • 2
    Electronic Resource
    Electronic Resource
    Investigation of synthesis and light stability of polymeric azo dyes. II. Polymeric acrylate-azo dyesPart I cf.3. (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 197 (1992), S. 175-184 
    Details
    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: Unterschiedlich 4′-substituierte 4-[N-Ethyl-N-(2-acryloyloxy)ethyl]aminoazobenzole dienten als Ausgangsmonomere für Homopolymerisationen und Copolymerisationen mit Styrol und Methylmethacrylat. Die Photobleichung der erhaltenen polymeren Azofarbstoffe (M̄ 4200-9000) wurde mittels einer Xenotest-Apparatur untersucht und mit den entsprechenden Monomeren verglichen. Es wird angenommen, daß die in der Reihenfolge monomerer  -  copolymerisierter  -  homopolymerisierter Azofarbstoff sinkende Photostabilität durch zunehmenden Energietransfer in der Matrix verursacht wird.
    Notes: Different 4′-substituted 4-[N-ethyl-N-(2-acryloyloxy)ethyl]aminoazobenzenes were used as starting monomers for homopolymerization and copolymerization reactions with styrene and methyl methacrylate. The photofading behaviour of the obtained polymeric azo dyes (M̄n 4200 - 9000) was investigated by means of a Xenotest device and compared with that of the corresponding monomers. The decreased photostability in the order monomer  -  copolymer  -  homopolymer was assumed to be caused by an increasing energy transfer in the matrix.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.051970115
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  • 3
    Electronic Resource
    Electronic Resource
    Stretching and overstretching of DNA in pulsed field gel electrophoresis. I. A quantitative study from the steady state birefringence decay (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1347-1357 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a sensitive birefringence instrument, the birefringence arising from the orientation of the DNA chain during electrophoretic transport has been recorded. This birefringence is shown to proceed both from the alignment (stretching) of the molecule in the direction of the electric field and from the extension of the length of its primitive path (overstretching). The contribution of these two processes can be separated in the decay of the birefringence after the end of the application of the electric field. The fast relaxation of the overstretching occurs first and is demonstrated to be the main contribution to the birefringence. The orientation factor of the remaining stretched state and its decay can be quantitatively understood using the biased reptation model. It provides, in addition, a high value for the tube diameter or gel pore size a (4500 ± 450 Å for a 0.7% agarose gel with a c-0.6g dependence in the agarose concentration cg) and a low value for the effective charge per base pair (0.2e as compared to 0.5e using the condensation hypothesis). The contribution of overstretching to the birefringence is also quantitatively interpreted in term of the change in the mean length l of DNA inside a pore size a. The dynamics of decay of this overstretching is well represented by a stretched exponential with a stretching exponent α = 0.44. The mean decay time decreases slightly with increasing fields and scales with the overall DNA length close to N20. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330905
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of proline-14 substitution on the secondary structure in a synthetic analogue of alamethicin (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 547-558 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Due to the bend introduced by proline 14 in the conformation of alamethicin (AcUPUAUQUVUGLUPVUUEQFol), the role of this residue was assumed essential in the barrel-stave model for voltage-gated ion channels. Taking advantage of a previous synthetic alamethicin analogue (L2) in which all eight α-aminoisobutyric(U) Were replaced by leucines (AcLPLALAQLVLGLLPVLLEQFol), another analogue (L5) was synthesized in order to test the effects ofproline-14 substitution by an alanine (AcLPLALAQLVLGLLPVLLEQFol). Previous conductance experiments showed that both high voltage dependence and multistate behavior were conserved. In order to complement these functional results, a conformational study of L5 has been undertaken and compared to L2 using CD. high field nmr, and molecular dynamics. Results show that L5 presents a better ordered structure than L2 particularly in the region of the substitution and in the C-terminal part. These results are discussed as regards the previous hypothesis of the nonessential character of helix bending for the gating of voltage-dependent ion channels. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360416
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  • 5
    Electronic Resource
    Electronic Resource
    Solid-state conformation of some basic sequential polypeptides (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1801-1808 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have studied the structure of solid films obtained by x-ray diffraction, from several basic polypeptides with a defined sequence. The alterating polypeptides poly(Ala-Lys), poly(Leu-Lys), poly(Val-Lys), and poly(Arg-Leu) all show a cross-β-structure in which layers of hydrophilic side chains alternate with layers containing hydrophobic side chains. The other polypeptides studied are not in the β-conformation and appear to be in the α-helical conformation. The helices obtained from poly(Lys-Ala-Ala) and poly(Lys-Ala-Ala-Lys) appear to be packed in an unusual fashion, which favors interaction between alanine side chains. Such behavior is not found in poly(Lys-Leu-Ala).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240910
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  • 6
    Electronic Resource
    Electronic Resource
    Stretching and overstretching of DNA in pulsed field gel electrophoresis. II. Coupling of orientation and transport in initial response to the field (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1359-1363 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rise of the birefringence following the application of an electric field to DNA in an agarose gel has been quantitatively analyzed to demonstrate the major role played by the chain overstretching. By analyzing the field free decay after short times, we demonstrate that the overshoot is completely due to overstretching. Its time of appearance τov varies with the field and DNA length in fair agreement with the E-lN0ln N0 prediction of Lim et al. [ (1990), Journal of Chemical Physics, Vol. 92, pp. 709-721]. The τov is also the time corresponding to one tube renewal after relaxation of the overstretching. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330906
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  • 7
    Electronic Resource
    Electronic Resource
    Modellbetrachtung zur Radikalausbeute bei der radikalischen Polymerisation (1974)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 3495-3502 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The kinetically effective radical efficiency is chemically and diffusion controlled. The proportion of each control mechanism characterizes the polymerizing system. The chemical control can be deduced from the chain initiation reaction, the diffusion control from the recombination reaction of the primary radicals. The model which is developed describes these competing reactions. The mean length of the diffusion path of the primary radicals is estimated.
    Notes: Die kinetisch wirksame Radikalausbeute ist eine chemisch und diffusionskontrollierte Größe. Der Grad der jeweiligen Kontrolle ist systemspezifisch. Die chemische Kontrolle geht hauptsächlich von der Kettenstartreaktion, die Diffusionskontrolle von der Primärradikalrekombination aus. Die entwickelte Modellvorstellung erfaßt diese konkurrierenden Einflüsse. Mittlere Diffusionswege der Primärradikale bis zu ihrer Rekombination werden abgeschätzt.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1974.021751215
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  • 8
    Electronic Resource
    Electronic Resource
    Study of the influence of stabilizers, metals, and peroxides on the thermo-oxidative degradation of poly(oxy-2,6-dimethyl-1,4-phenylene) (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 1961-1971 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The authors have studied the influence of some stabilizers, trace amounts of cupric and ferric compounds, and peroxides on the thermo-oxidative degradation of poly(oxy-2,6-dimethyl-1,4-phenylene). It was found that phenolic antioxidants, didodecyl 3,3′-thiodipropionate, and phosphorous acid esters do not exhibit a stabilizing effect. 2-Benzimidazolethiol, 2-benzothiazolethiol, and hexamethylphosphoric triamide were found to be retardation agents. Based on these results a mechanism of the degradation process is proposed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820709
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular weight distributions, 3Part 2: cf.7. Gamma-ray induced polymerization of methyl methacrylate in the solid state (1980)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 1727-1735 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics and molecular weight distributions of the gamma-ray induced polymerization of methyl methacrylate were investigated in the solid state in the temperature range of -50°C to -65°C. The polymerization reaction rate was found to be proportional to the amount of polymer formed. The polymerization at the freezing point did not show any special features. With increasing dose rate the radiation efficiency was found to drop faster in the solid than in the liquid state. The molecular weights showed the same features as in the liquid state polymerization previously reported and increased with percent conversion. A kinetic model for the solid state polymerization is proposed. The molecular weight distribution function could be expressed by a log-normal distribution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1980.021810815
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  • 10
    Electronic Resource
    Electronic Resource
    Über die elementarreaktionen der radikalischen polymerisation von benzylmethacrylat (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 173 (1973), S. 101-112 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The influence of various solvents on the rate constants of chain growth and chain termination of benzyl methacrylate has been determined. The absolute rate constants were obtained by combination of stationary and nonstationary methods (rotating sector).The initiator efficiency f depends on the viscosity of the monomer solvent system and on the type of monomer. f is nearly independent of the monomer concentration and of the initiation rate. From that one may conclude that a considerable proportion of the twin recombination reactions takes place outside the primary cage formed by the solvent.The rate constant of chain growth kw is nearly identical to kw of methyl methacrylate and shows a slight increase with increasing solvent viscosity. This has been found in the case of methyl methacrylate too. The rate constant of chain termination ka increases less than proportionally to the reciprocal value of the viscosity of the monomer solvent system. A possible correlation to the internal viscosity is discussed.
    Notes: Durch Kombination stationärer und instationärer Methodik (rotierender Sektor) werden die Absolutwerte der Geschwindigkeitskonstanten von Kettenwachstum und Kettenabbruch von Benzylmethacrylat unter dem Einfluß verschieden viskoser Lösungsmittel bestimmt.Die Radikalausbeute f hängt von der Viskosität des Lösungssystems und der Art der Monomeren, dagegen nicht (oder fast nicht) von der Konzentration des Monomeren und der Geschwindigkeit der Radikalerzeugung ab. Daraus wird geschlossen, daß ein merklicher Anteil von Zwillingsrekombinationen außerhalb des primären Lösungsmittelkäfigs stattfindet.Die Geschwindigkeitskonstante kw des Kettenwachstums stimmt praktisch überein mit der des Methylmethacrylats und zeigt ebenfalls einen leichten Anstieg mit der Lösungsmittel-viskosität. Die Geschwindigkeitskonstante ka des Kettenabbruchs nimmt etwas schwächer als proportional der reziproken Viskosität der Monomer-Lösungsmittel-Viskosität zu. Es wird auf den möglichen Einfluß der inneren Viskosität hingewiesen.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021730107
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