Jump to main content
Jump to site search

Issue 20, 2019
Previous Article Next Article

Effects of mono- and divalent cations on the structure and thermodynamic properties of polyelectrolyte gels

Author affiliations

Abstract

Measurements are reported on the effect of monovalent and divalent salts on the swelling behavior and supramolecular structure of sodium polyacrylate gels (NaPA) made by osmotic swelling pressure and small angle neutron scattering measurements. The swelling response of the gels in solutions of ten different monovalent salts is found to be practically identical indicating that the principal effect of monovalent ions is screening the electrostatic repulsion among the charged groups on the polyelectrolyte chains; i.e., chemical differences between the monovalent ions do not play a significant role. Introducing Ca2+ ions into the equilibrium NaCl solution results in a sharp volume transition of the gels. The threshold Ca2+ ion concentration at which the transition occurs increases with increasing NaCl concentration in the surrounding bath. It is demonstrated that the swelling behavior of NaPA gels exhibits universal properties in solutions containing both NaCl and CaCl2. Osmotic swelling pressure measurements reveal that both the second and third virial coefficients decrease with increasing CaCl2 concentration until the volume transition is reached. The macroscopic measurements are complemented by small angle neutron scattering that reveals the variation of the thermodynamic length scales as the volume transition is approached. The thermodynamic correlation length L increases with increasing CaCl2 concentration.

Graphical abstract: Effects of mono- and divalent cations on the structure and thermodynamic properties of polyelectrolyte gels

Back to tab navigation

Article information


Submitted
04 Mar 2019
Accepted
27 Apr 2019
First published
07 May 2019

Soft Matter, 2019,15, 4153-4161
Article type
Paper

Effects of mono- and divalent cations on the structure and thermodynamic properties of polyelectrolyte gels

M. Mussel, P. J. Basser and F. Horkay, Soft Matter, 2019, 15, 4153
DOI: 10.1039/C9SM00464E

Social activity

Search articles by author

Spotlight

Advertisements