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  • 1
    Electronic Resource
    Electronic Resource
    The effect of topological constraints on polymer network pressure (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1833-1841 
    Details
    ISSN: 0887-6266
    Keywords: polymer gels ; topological constraints ; osmotic deswelling ; polyelectrolytes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent data on comparative osmotic deswelling of poly(acrylic acid) gels and solutions shows that the difference between osmotic pressure of the gel and of the solution, Pgel (c, f) - Psolution (c, f), taken at equal polymer concentration (c) and fraction of the ionized acrylic acid monomers (f), changes its sign from negative to positive as the concentration c increases; this effect is enhanced with increasing f whereby it is shifted toward lower concentrations. In order to explain this effect, a model is suggested for the elastic pressure of the gel network which takes into account the effect of topological constraints combined with the effect of network ionization. According to the model, the sign-change of Pgel - Psolution originates from the topological constraints on conformations of the network; the ionization of the network chains enhances this effect and shifts it to the concentration range of the experiment. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1833-1841, 1997
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Osmotic deswelling of weakly charged poly(acrylic acid) solutions and gels (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2269-2279 
    Details
    ISSN: 0887-6266
    Keywords: poly(electrolyte) ; gel ; osmotic deswelling ; poly(acrylic acid) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The osmotic pressure of weakly charged aqueous poly(acrylic acid) (PAA) solutions and the swelling pressure PAA gels were studied by osmotic deswelling at different degrees of ionization (α). In solution, the osmotic pressure was found to scale linearly with concentration, whereas the scaling power of the swelling pressure of gels was higher (1.66). The effect of the ionization degree on the osmotic coefficient in PAA solutions was in agreement with the theory of Borue and Erukhimovich [Macromolecules, 21, 3240 (1988)]. Ionization increases the swelling capacity of the PAA gels until a plateau is reached at about 35% neutralization. The concentration at equilibrium swelling scales as Ce ∼ α-0.6. The contribution of the network to the gel swelling pressure is evaluated by subtracting the osmotic pressure of the polymer solution at the same concentration and degree of ionization. In swollen gels the extended network opposes swelling. As the gel is osmotically deswelled, a state of zero network pressure exists at a certain concentration, below which the network elasticity favors swelling. The crossover concentration shifts to lower values as the degrees of ionization increases. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331612
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