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NMR water self-diffusion and relaxation studies on sodium polyacrylate solutions and gels in physiologic ionic solutions

Authors

  • Ruiliang Bai,

    Corresponding author
    1. Section on Tissue Biophysics and Biomimetics, Program in Pediatric Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
    2. Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland
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  • Peter J. Basser,

    1. Section on Tissue Biophysics and Biomimetics, Program in Pediatric Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
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  • Robert M. Briber,

    1. Department of Materials Science and Engineering, University of Maryland, College Park, Maryland
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  • Ferenc Horkay

    1. Section on Tissue Biophysics and Biomimetics, Program in Pediatric Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
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ABSTRACT

Water self-diffusion coefficients and longitudinal relaxation rates in sodium polyacrylate solutions and gels were measured by NMR, as a function of polymer content and structure in a physiological concentration range of monovalent and divalent cations, Ca2+ and Na+. Several physical models describing the self-diffusion of the solvent were applied and compared. A free-volume model was found to be in good agreement with the experimental results over a wide range of polymer concentrations. The longitudinal relaxation rate exhibited linear dependence on polymer concentration below a critical concentration and showed non-linear behavior at higher concentrations. Both the water self-diffusion and relaxation were less influenced by the polymer in the gel state than in the uncrosslinked polymer solutions. The effect of Na+ on the mobility of water molecules was practically undetectable. In contrast, addition of Ca2+ strongly increased the longitudinal relaxation rate while its effect on the self-diffusion coefficient was much less pronounced. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40001.

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