Non-swellability of polyelectrolyte gel in divalent salt solution due to aggregation formation. (26th May 2022)

• Record Type: Journal Article
• Authors: Tang, Jian; Katashima, Takuya; Gupit, Caidric Indaya; Li, Xiang; Mitsukami, Yoshiro; Yokoyama, Yuki; Sakumichi, Naoyuki; Chung, Ung-il; Shibayama, Mitsuhiro; Sakai, Takamasa
• Is Part Of: Polymer. Volume 250(2022)
• Publication Date: 2022-05-26
• Subjects: Polyelectrolyte -- Polymer gel -- Swelling -- Donnan equilibrium -- Counterion condensation; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2022.124894
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: The swelling behavior of polyelectrolyte gels depends on their ambient conditions owing to the ionic pressure of the Gibbs‒Donnan equilibrium. In a polyelectrolyte gel with a high fixed ion density, the counterion condensation effect influences the Gibbs‒Donnan equilibrium. In particular, the mechanism of the divalent salt effect remains unclear due to its complexity. This study investigated the swelling properties of polyelectrolyte gels in a divalent CaCl2 salt solution using model polyelectrolyte gels called tetra-polyacrylic acid-polyethylene glycol gels (Tetra-PAA-PEG gels). In [Ca 2+ ] < 0.1 mM, the swelling ratios increased with increasing pH. With increasing Ca 2+ ions concentration, the gel showed the non-swellability independent of pH, which cannot be described by the simple mean-field theories. The viscoelastic and small-angle X-ray scattering measurements indicate that an aggregation formation due to the divalent salt induces an anomaly even in the model system. These findings will help understand the swelling behavior of polyelectrolyte gels in divalent salt systems. Graphical abstract: Image 1 Highlights: Design of a model polyelectrolyte gel with alternating neutral and charged sequences. Non-swellability was achieved in divalent salt solution even using the model system. Well-disperse sphere structures were constructed by divalent salt. Divalent salt-induced structural change resulting into non-swellability.