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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2665-2670 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The swelling behavior of weakly crosslinked polyelectrolyte gels based on sodium methacrylate (PMA) and diallyldimethylammonium chloride (DADMAC) in aqueous medium was studied in the presence of different types of salts (NaCl, arginine hydrochloride, cetylpyridinium chloride (CPC), sodium dodecyl sulfate (SDS), and sodium dodecylbenzenesulfonate (SDBS)). It is shown that, starting from some characteristic concentration of a salt, a further increase of the salt concentration results in the shrinking of the gels. This characteristic concentration is defined by the gel parameters (polymer concentration in the gel that is a function of the monomer concentration at the conditions of hydrogel synthesis) and does not depend on the kind of salt used, except for the system polyelectrolyte gel/oppositely charged surfactant (PMA-CPC and DADMAC-SDS or SDBS). It is shown that the initial rate of gel shrinking for all studied systems, including the system gel/oppositely charged surfactant, is determined by the salt concentration and the gel parameters. For the systems PMA-CPC and DADMAC-SDS the gel collapse is a two-step process.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 555-558 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 51-60 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied theoretically the behavior of a collapsed persistent macromolecule in poor solvent as a model of collapse transition of single double-stranded DNA chain, and constructed the diagram of states in the variables with contour length of a macromolecule and quality of the solvent. We found that the state of toroidal globule exists as an intermediate state between the states of elongated coil state and the spherical globule. Our theoretical result suggests that a single linear macromolecule with a high degree of polymerization can form a toroidal globule. However, the range in which the toroidal structure is stable decreases as the macromolecule length increases. Experimental observation with transmission electron microscopy has been performed to study the globular structure of single DNA chain (bacteriophage T4 DNA, λ-DNA) collapsed by hexammine cobalt (III) at different concentrations. We found that an extremely long chain of T4 DNA (166 kbp), with a contour length of 56 μm, actually forms a toroidal globule, and that isotropic spherical globule appears at higher hexammine cobalt concentration. © 1997 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0887-6266
    Keywords: polyelectrolyte gel ; surfactant ; self-assembly ; nanostructure ; X-ray scattering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Interaction of slightly crosslinked hydrogels of poly(diallyldimethylammonium chloride) (PDADMACI) and of copolymer DADMACI/acrylamide (AAm) with sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfate (SDBS) results in significant shrinking of the gels due to the formation of polymer-surfactant complexes. Jump-wise transitions in the collapsed state were observed for the networks with the content of cationic groups 100 and 75 mol %. The structure of complexes was studied by means of X-ray scattering method. The scattering curves for collapsed gels, where most chloride anions were replaced by anions of SDS, show a set of well-pronounced narrow diffraction maxima. Fully charged “wet” complexes studied at the equilibrium swelling conditions exhibit high degree of ordering, which diminishes upon drying with the simultaneous transition from hexagonal to lamellar type of ordering. In contrast to this, for DADMACl/AAm copolymer gels (75 mol % of DADMACl monomers in the initial polymerization mixture) the ordering is less pronounced in the “wet” state and becomes more perfect upon drying. The SDS aqueous solutions of the same concentration in the absence of gel do not show such high degree of ordering, while the system of SDS/neutral AAm gel exhibits lamellar ordering typical for low-temperature phases of SDS solutions. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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