Influence of Divalent Ions on Composition and Viscoelasticity of Polyelectrolyte Complexes
ORAL
Abstract
The addition of monovalent salts to polyelectrolyte complexes (PECs) comprising oppositely charged polyelectrolytes is known to result in diminishing propensity for complexation, leading to complexes with higher water contents and lower moduli. However, the influence of multivalent ions on polyelectrolyte complexation beyond enhanced screening effects has not yet been explored. In this presentation, significant impact of salt cation valency on the composition, ion partitioning, and viscoelasticity of charge-matched PECs will be discussed. Preferential partitioning of divalent cations (Ca2+ and Sr2+) into the complex phase will be shown to stand in stark contrast to depletion of monovalent ions (Na+) from the complexes. Concomitantly, electrostatic bridging of polyanion chains by divalent cations will be described to result in hindered chain relaxation, manifesting as a non-monotonic evolution of the shear moduli of the complexes with increasing divalent salt concentrations. Relatedly, a failure of time-salt and time-ionic strength superposition approaches in presence of divalent ions will be demonstrated, underscoring the non-trivial influence of these ions on chain relaxation behavior.
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Presenters
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Divya Iyer
University of California, Los Angeles
Authors
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Divya Iyer
University of California, Los Angeles
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Vaqar Syed
University of California, Los Angeles
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Samanvaya Srivastava
UCLA, Department of Chemical and Biomolecular Engineering, University of California, Los Angeles. Los Angeles, CA 90095, University of California, Los Angeles