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  • Polymer and Materials Science  (3)
  • 13C—1H—{1H} three-spin effects
  • Wiley-Blackwell  (3)
  • 1985-1989  (3)
  • 1985  (3)
Collection
Keywords
Publisher
  • Wiley-Blackwell  (3)
Years
  • 1985-1989  (3)
Year
  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Chemical heterogeneity of a partially modified dextran with ethyl carbonate groups (1985)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 135 (1985), S. 139-149 
    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: Eine Probe von mit Ethylcarbonatgruppen teilweise modifiziertem Dextran wurde kreuz-fraktioniert. Auf der Basis von Trübungspunkt-Messungen wurden zwei Systeme gewählt: THF/Hexan und DMF/0,5 proz. wässerige NaCl-Lösungen. Die chemische Zusammensetzung (CCD) und die Molekulargewichtsverteilung (MWD) wurden den Fraktionierungsdaten entnommen. Die beobachtete chemische Heterogenität kann mit der Art des Reaktionsmechanismus von Dextran und Ethylchlorformiat korreliert werden. Die kumulativen Fraktionierungsdaten wurden nach den Zwei-Parameter-Funktionen von Tung und Wesslau angepasst.
    Notes: A sample of a partially modified dextran with ethyl carbonate groups was fractionated by cross-fractionation. Two systems THF/hexane and DMF/0.5% aqueous NaCl were selected on the basis of cloud-point determinations. The chemical composition distribution (CCD) and molecular weight distribution (MWD) curves were constructed from fractionation data. The chemical heterogeneity observed may be correlated with the pattern of reaction of dextran with ethyl chloroformate. The cumulative data were fitted by the two-parameter MWD functions of Tung and of Wesslau.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1985.051350112
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