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Issue 21, 2011
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Effect of ionic strength and type of ions on the structure of water swollen polyelectrolyte multilayers

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Abstract

This study addresses the effect of ionic strength and type of ions on the structure and water content of polyelectrolyte multilayers. Polyelectrolyte multilayers of poly(sodium-4-styrene sulfonate) (PSS) and poly(diallyl dimethyl ammonium chloride) (PDADMAC) prepared at different NaF, NaCl and NaBr concentrations have been investigated by neutron reflectometry against vacuum, H2O and D2O. Both thickness and water content of the multilayers increase with increasing ionic strength and increasing ion size. Two types of water were identified, “void water” which fills the voids of the multilayers and does not contribute to swelling but to a change in scattering length density and “swelling water” which directly contributes to swelling of the multilayers. The amount of void water decreases with increasing salt concentration and anion radius while the amount of swelling water increases with salt concentration and anion radius. This is interpreted as a denser structure in the dry state and larger ability to swell in water (sponge) for multilayers prepared from high ionic strengths and/or salt solution of large anions. No exchange of hydration water or replacement of H by D was detected even after eight hours incubation time in water of opposing isotopic composition.

Graphical abstract: Effect of ionic strength and type of ions on the structure of water swollen polyelectrolyte multilayers

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Publication details

The article was received on 28 Jul 2010, accepted on 31 Mar 2011 and first published on 26 Apr 2011


Article type: Paper
DOI: 10.1039/C0CP01357A
Phys. Chem. Chem. Phys., 2011,13, 10318-10325

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    Effect of ionic strength and type of ions on the structure of water swollen polyelectrolyte multilayers

    S. Dodoo, R. Steitz, A. Laschewsky and R. von Klitzing, Phys. Chem. Chem. Phys., 2011, 13, 10318
    DOI: 10.1039/C0CP01357A

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