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Issue 12, 2018
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Competitive calcium ion binding to end-tethered weak polyelectrolytes

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We have developed a molecular model to describe the structural changes and potential collapse of weak polyelectrolyte layers end-tethered to planar surfaces and spherical nanoparticles as a function of pH and divalent ion concentration. In particular, we describe the structural changes of polymer-coated nanoparticles end-tethered to copolymers of poly(acrylic acid) (pAA) and poly arcrylamido-2-methylpropane sulfonate (pAMPS) in the presence of Ca2+ ions. We find that end-grafted poly(acrylic acid) layers will collapse in aqueous solutions containing sufficient amounts of Ca2+ ions, while polymers and copolymers with sufficient AMPS monomers will not collapse. The collapse of end-tethered pAA is due to the formation of calcium bridges between two acrylic acid monomers and one calcium ion. On the other hand pAMPS layers do not collapse due to the lack of calcium bridges. The collapse of pAA layers is strongly dependent on the pH as well as divalent and monovalent salt concentrations of the environment. The collapse is also strongly influenced by the curvature of the tethering surface.

Graphical abstract: Competitive calcium ion binding to end-tethered weak polyelectrolytes

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The article was received on 11 Dec 2017, accepted on 06 Feb 2018 and first published on 12 Feb 2018

Article type: Paper
DOI: 10.1039/C7SM02434G
Soft Matter, 2018,14, 2365-2378

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    Competitive calcium ion binding to end-tethered weak polyelectrolytes

    R. J. Nap, S. H. Park and I. Szleifer, Soft Matter, 2018, 14, 2365
    DOI: 10.1039/C7SM02434G

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