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  • Chemistry  (290)
  • Physical Chemistry  (13)
  • 13C—1H—{1H} three-spin effects
  • Wiley-Blackwell  (291)
  • 11
    Electronic Resource
    Electronic Resource
    Water-insoluble dextrans by grafting, 2Part 1: cf.3.. Reaction of dextrans with n-alkyl chloroformates. Chemical and enzymatic hydrolysis (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 17-29 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work deals with the modification reaction of dextran with ethyl and butyl chloroformate using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analyses. The reaction rate was found to increase in the following order: N,N′-dimethylaniline 〈 pyridine 〈 triethylamine. The presence of cyclic carbonates was observed when triethylamine was used as catalyst. A linear dependence of the reaction rate on polymer and pyridine concentrations and a more complex dependence on the n-alkyl chloroformate concentration were found. Reaction rate and yield decrease with increasing amount of LiCl in the solvent medium and increase with increasing chain length of the n-alkyl chloroformate. The activation energy was found to be 64 kJ/mol (15,3 kcal/mol). The equilibrium water content (EWC) values decreases progressively when either the content of carbonate groups or the side chain length increases. The hydrolysis in the heterogeneous phase showed that the time required for the polymer solubilization is dependent upon the nature of the carbonate groups, the temperature as well as the pH value of the medium. Dextranase was found to be inactive in the hydrolysis of water-insoluble modified dextrans. However, the hydrolysis takes place when water-soluble modified dextrans were used.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860103
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  • 12
    Electronic Resource
    Electronic Resource
    Synthesis and hydrolysis of esters from amylose and nicotinoyl chloride (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 2269-2274 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The modification reaction of amylose with nicotinoyl chloride using pyridine as catalyst was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on polymer, nicotinoyl chloride and pyridine was found. The activation energy was found to be 32,2 kJ/mol. The hydrolysis in the heterogeneous phase showed that the release of the active compound is dependent upon the hydrophilic character of the modified amylose polymers, the temperature as well as the pH value of the medium.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021891006
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  • 13
    Electronic Resource
    Electronic Resource
    Study of the distributions of chemical composition and molecular weight in relation to the preparation method of vinyl alcohol/vinyl acetate copolymers (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 1215-1228 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The chemical heterogeneity of two vinyl alcohol/vinyl acetate (VAL-VAC) copolymers prepared by partial acetylation of poly(vinyl alcohol) and by partial alkaline hydrolysis of poly(vinyl acetate), respectively, was studied by cross-fractionation. The used solvent/non-solvent systems were selected on the basis of cloud-point determinations. The chemical composition distribution (CCD) and the molecular weight distribution (MWD) curves were constructed from fractionation data. The observed chemical heterogeneity was correlated with the kinetic parameters of the two different methods used for the preparation of the VAL-VAC copolymers. Thus, squared standard deviation values \documentclass{article}\pagestyle{empty}\begin{document}$\overline {{\rm \sigma }^{2} }$\end{document}= 2,90·10-4 and \documentclass{article}\pagestyle{empty}\begin{document}$\overline {{\rm \sigma }^{2} }$\end{document}= 7,42·10-4 were found for the two VAL-VAC copolymers prepared by acetylation and hydrolysis, respectively. These results are in agreement with theoretical predictions. The cumulative data were fitted by the two-parameters MWD functions of Tung and of Wesslau.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021870518
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  • 14
    Electronic Resource
    Electronic Resource
    Water-insoluble dextrans by grafting, 3Part 2: cf.2.. Reaction of dextran with butyl isocyanate. Chemical hydrolysis (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 2831-2838 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The modification reaction of dextran with butyl isocyanate using 1,4-diaza[2.2.2]bicyclooctane as catalyst was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy as well as by chemical analysis. A linear dependence of the reaction rate on the concentrations of polymer, butyl isocyanate and catalyst was found. The activation energy was found to be 38,5 kJ/mol (9,2 kcal/mol). The homogeneous hydrolysis in alkaline medium was found to be first order with respect to both the base and the butyl urethane concentrations. The activation energy, obtained for the base catalyzed homogeneous hydrolysis, was 83,7 kJ/mol (20,0 kcal/mol). The heterogeneous hydrolysis of a water insoluble modified dextran (degree of substitution = 0,72) showed that no hydrolysis takes place under the applied conditions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021881205
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  • 15
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of 2-acetoxybenzoic acid-dextran ester conjugates (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 2391-2396 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work deals with the modification reaction of dextran with 2-acetoxybenzoyl chloride (acetylsalicyloyl chloride) using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy. Transesterification reactions were observed when 4-dimethylaminopyridine or pyridine were used as catalysts, with the formation of acetoxy, 2-hydroxybenzoyloxy (salicyloyloxy) and 2-acetoxybenzoyloxy (acetylsalicyloxy) groups. When triethylamine was used as catalyst, only acetylsalicyloyloxy groups were found to be grafted onto the polymer chain. A linear dependence of the reaction rate on the concentrations of polymer, acetylsalicyloyl chloride and triethylamine was found. The activation energy was found to be 13,8 kJ/mol.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021901005
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  • 16
    Electronic Resource
    Electronic Resource
    Synthèse et réactions photochimiques d'homopolymères et de copolymères de la p-vinylbenzophénone et du vinylferrocènePartie de la thèse soutenue par G. Sánchez devant l'Université Strasbourg I, Louis Pasteur. (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 131-146 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(p-vinylbenzophenone), (poly[1-(4-benzoylphenyl)ethylene]), (PVB) has been synthesized for the first time directly from its monomer p-vinylbenzophenone (VB) the preparation of which was improved. In a second step, copolymers containing blocks of photosensitive VB units separated by isolated quenching vinylferrocene (VF) units have been prepared. PVB and the VB-VF copolymers were irradiated in the presence of isopropyl alcohol in benzene solutions. The benzophenone groups inserted in these macromolecular chains obey the same reaction scheme as the photoreduction of the small molecule of benzophenone. However, recombination of the radicals located along the polymeric chain leads to intra- and intermolecular reactions changing drastically the macromolecular morphology by the formation of cycles and networks and by chain scissions. The quantum yields of the photochemical transformations were measured, but they could not be related quantitatively to morphological parameters. In all cases the ferrocene group inhibits strongly the photochemical reaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1978.021790113
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  • 17
    Electronic Resource
    Electronic Resource
    Mechanical properties of chitosan films: Effect of solvent acid (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 1353-1359 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The apparent Young's modulus shows a linear relationship with junction density of chitosan films. The linear relationship of apparent Young's modulus with chitosan concentration is also observed. The linear relationship depends of the acid used in the casting solution. Relaxation times were of the order of 104 seconds, indicating a slow physical process. Stress-relaxation behavior of swollen chitosan films, prepared by solvent casting from dilute acetic or propionic acid solutions, can be represented by a one-component Maxwell model.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021830528
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  • 18
    Electronic Resource
    Electronic Resource
    Sequence distribution and glass transition of vinyl alcohol/n-alkyl vinyl carbonate copolymers (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 2153-2159 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 13C NMR spectroscopy was used for the determination of the sequence distribution in vinyl alcohol-ethyl vinyl carbonate copolymers prepared by reaction of poly(vinyl alcohol) with ethyl chloroformate. The 13C NMR spectra of the methylene carbons in the main chain show three split peaks whose intensities change with copolymer composition. These peaks can be assigned to the three dyad sequences. The obtained results show that ethyl vinyl carbonate units have an alternating tendency in the copolymer chain. The Tg values of the vinyl alcohol-ethyl vinyl carbonate and vinyl alcohol-butyl vinyl carbonate copolymers are influenced by both the overall copolymer composition and the monomer sequence distribution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021851010
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  • 19
    Electronic Resource
    Electronic Resource
    Release of sodium salicylate from vinyl alcohol/n-alkyl vinyl carbonate copolymers (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 2117-2123 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This study is concerned with the sodium salicylate release from thin discs of vinyl alcohol/n-alkyl vinyl carbonate copolymers into an aqueous medium under sink conditions. The drug content of the disc decreases with pseudo-first order rate initially, whereas the drug quantity released is proportional to the square root of time. Data analysis supported the latter treatment, which is in agreement with the diffusional matrix model and invalidates the pseudo-first order assumption. The diffusion coefficient D of vinyl alcohol/ethyl vinyl carbonate copolymers decreases with increasing ethyl vinyl carbonate content whilst D increases as both sodium salicylate concentration and temperature increase. The activation energy of diffusion was found to be 46,03 kJ/mol (11,00 kcal/mol).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021861015
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  • 20
    Electronic Resource
    Electronic Resource
    Synthesis and controlled release behaviour of esters from amylose and 1-naphthylacetyl chloride (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 1513-1518 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work deals with the modification reaction of amylose with 1-naphthylacetyl chloride using pyridine as catalyst and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by IR, 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on the concentration of polymer, 1-naphthylacetyl chloride and pyridine was found. The activation energy was found to be 32,4 kJ/mol. The hydrolysis in the heterogeneous phase showed that the release of the active compound from tablets is dependent on the hydrophilic character of the modified amylose as well as on the pH value of the medium.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910704
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