Issue 8, 2015

On the crossroads of current polyelectrolyte theory and counterion-specific effects


Aqueous solutions of polyelectrolytes are studied here by means of neutron scattering, with emphasis on backbone hydrophobicity and counter ion specific effects. Ionene polyelectrolytes with varying chain charge density and different counter ions are considered. Their neutron scattering data feature a number of aspects and trends that clearly deviate from the predictions of the existing theory. Ionenes challenge the current hydrophilic–hydrophobic classification of water-soluble polyelectrolytes. The hydrophobic character of their hydrocarbon backbone emerges only for very low chain charge densities (at 15% of charged monomers), which is significantly lower than for other polyelectrolytes with a more complex structure. Universality in the counter ion specific effect seen in ionene solutions with Br or F counterions is established. The polyelectrolyte peak in the scattering spectra of Br-ionenes disappears beyond a specific charge concentration, which is identical across all ionene chain charge densities. In addition, scattering spectra of Br-ionenes and F-ionenes feature contrasting temperature trends, which are accentuated with decreasing chain charge density. Our interpretation of the F–Br effect, based on the different hydration properties of the counter ions, is supported by additional NMR measurements on ionenes with mixed counter ion clouds. Overall, the study of ionene polyelectrolytes points clearly to the need for combining the scaling concepts with those of ion specificity, to obtain a theoretical framework encompassing the wealth of phenomena occurring in polyelectrolyte solutions.

Graphical abstract: On the crossroads of current polyelectrolyte theory and counterion-specific effects

Supplementary files

Article information

Article type
24 Nov 2014
12 Jan 2015
First published
15 Jan 2015
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2015,17, 5650-5658

Author version available

On the crossroads of current polyelectrolyte theory and counterion-specific effects

N. Malikova, A. Rollet, S. Čebašek, M. Tomšič and V. Vlachy, Phys. Chem. Chem. Phys., 2015, 17, 5650 DOI: 10.1039/C4CP05469E

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