Effects of mono- and divalent cations on the structure and thermodynamic properties of polyelectrolyte gels
| Autor: | Matan Mussel, Ferenc Horkay, Peter J. Basser |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
chemistry.chemical_classification
Sodium polyacrylate Analytical chemistry 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Small-angle neutron scattering Article Polyelectrolyte 0104 chemical sciences Divalent Ion chemistry.chemical_compound Volume (thermodynamics) chemistry Virial coefficient medicine Swelling medicine.symptom 0210 nano-technology |
| Zdroj: | Soft Matter |
| ISSN: | 1744-6848 1744-683X |
| DOI: | 10.1039/c9sm00464e |
| Popis: | 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 Ca(2+) ions into the equilibrium NaCl solution results in a sharp volume transition of the gels. The threshold Ca(2+) 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 CaCl(2). Osmotic swelling pressure measurements reveal that both the second and third virial coefficients decrease with increasing CaCl(2) 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 CaCl(2) concentration. |
| Databáze: | OpenAIRE |
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