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  • 1
    Electronic Resource
    Electronic Resource
    Investigations on nylon 4 membranes. Synthesis and transport properties. I. Synthesis of nylon 4 polymerPresented at the IUPAC 26th International Symposium on Macromolecules, Mainz, West Germany, September 17-21, 1979. (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1135-1142 
    Details
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: The synthesis of nylon 4 (polypyrrolidone) by the anionic polymerization of 2-pyrrolidone through the use of the CO2/potassium pyrrolidonate catalyst system for use in preparing polymer membranes for separation purposes was investigated in detail. The effects of the quantity of CO2, the potassium pyrrolidonate catalyst, and the reaction temperature on the yield and molecular weights of the nylon 4 were studied. At reaction temperatures of 50°C and a reaction time of 120 hr, a yield of 50.9% with intrinsic viscosity of 4.42 (corresponding to Mn of 108,200 and Mw of 135,850) was obtained. The molecular weight distributions of the nylon 4 were determined by gel permeation chromatography (GPC) using m-cresol as the eluting solvent and were found to have a relatively narrow distribution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260407
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  • 2
    Electronic Resource
    Electronic Resource
    Investigations on nylon 4 membranes: Synthesis and transport properties. II. Transport properties of nylon 4 polymer membranesPresented at the IUPAC, 26th International Symposium on Macromolecules, Mainz, West Germany, Sept. 17-21, 1979. (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1907-1918 
    Details
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: The reverse osmosis, ultrafiltration, and dialysis properties of nylon 4 membranes to separations of sodium chloride, urea, a series of ethylene glycols and other compounds in the aqueous phase were investigated. The nylon 4 membranes were prepared from a formic acid solution with and without organic or inorganic additives. The effects of polymer concentration, amount of additives, casting time, and temperature on the membrane performance in terms of salt separation and product rate were investigated. The tensile properties of the nylon 4 membranes in both the dry and wet states were determined. It was found that the highest salt separation of a 0.1% sodium chloride solution did not exceed 53.3%. However, these membranes showed some intersting dialysis properties which were comparable to those of commercial cellophane and cellulose acetate membranes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260615
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  • 3
    Electronic Resource
    Electronic Resource
    Incorporating solvation effects into density functional theory: Calculation of absolute acidities (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 61 (1997), S. 207-217 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An approach to the calculation of molecular electronic structures, solvation energies, and pKa values in condensed phases is described. The electronic structure of the solute is described by density functional quantum mechanics, and electrostatic features of environmental effects are modeled through external charge distributions and continuum dielectrics. The reaction potential produced by a mode of the molecular charge distribution is computed via finite-difference solutions to the Poisson-Boltzmann equation and incorporated into the self-consistent field procedure. Here we report results on three sets of organic acids, whose pKa values range over 16 pH units. The first set provides models for ionizable side chains in proteins; the second set considers the effects of substituting one to three chlorine atoms for hydrogens in acetic acid; and the final set consists of 4-substituted-bicyclo-[2.2.2]-octanecarboxylic acids. Successful prediction of “absolute” pKa values places stringent requirements on the computation of gas-phase proton affinities and on the response to solvation. In some cases the current model shows substantial errors, but overall the results and trends are in good agreement with experiment. Prospects for extending this approach to more complex systems such as proteins are briefly discussed. © 1997 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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