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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 179-192 
    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: Crosslinked poly(acryloylmorpholines) have been prepared in bead form by suspension polymerization of N-acryloylmorpholine and N,N′-methylenediacrylamide, respective molar ratios 10/1, in aqueous solution dispersed in liquid paraffin. The swelling properties of beads of two porosities, designated Enzacryl Gel K1 and Enzacryl Gel K2, were measured in a range of common solvents. Gels derived by swelling in both chloroform and tetrahydrofuran were evaluated as column packings for gel permeation chromatography. For Enzacryl Gel K1 and polystyrene solutes, molecular weight exclusion limits of approximately 4 × 103 and 6 × 102 were observed in chloroform and tetrahydrofuran, respectively. In the case of Enzacryl Gel K2, the corresponding exclusion limits were 104 and 5 × 103. Molecular weight fractionation ranges for both polystyrenes and polyethylene glycols are discussed in terms of gel structure.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Detailed potentiometric titration curves have been obtained for poly(acrylic acid) (Mn = 2.6 × 106) in solution at four different ionic strengths at 25°C. When plotted as pH + log [(1 - α)/α] versus α (where α is the degree of dissociation), they reveal the presence of two different molecular conformations, denoted PAA(a) and PAA(b), with a transition between them. The proportion of the material present in the two conformations has been calculated for different degrees of dissociation and is found to be independent of ionic strength. PAA(a) is intact up to α = 0.22 and is completely converted into PAA(b) by α = 0.75. The free energy of transition from PAA(a) to PAA(b) when both forms are uncharged decreases numerically from -275 to -157 cal./mole monomer residues as the ionic strength increases from 0.02 to 0.20. The increase of the pH of solutions of the PAA(a) from over those of the PAA(b) form at a given value of α, is largely independent of α. This makes it possible to calculate the free energy of transition from PAA(a) to PAA(b) when both forms are charged to the same extent. This free energy is proportional to α and decreases numerically from -944α to -561α (cal.) as ionic strength increases from 0.02 to 0.20. The charge-independent part of the free energy of transition is a constant fraction of the total, at a given value of α, independent of the ionic strength. The PAA(a) form is the more compact, less contractile, and more ordered structure. The possibility is suggested that this conformation may be partly helical in nature.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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