Equilibrium swelling properties of poly( N-vinylimidazole-co-sodium styrenesulfonate) hydrogels

• Published in: European polymer journal Vol. 37; no. 12; pp. 2345 - 2352
• Main Authors: Valencia, Joaquı́n, Piérola, Inés F.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2001; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Hydrogels; Ionic crosslink; Organic polymers; Physicochemistry of polymers; Poly( N-vinylimidazole-co-sodium styrenesulfonate); Polyampholitic gel; Properties and characterization; Solution and gel properties; Swelling; Poly( N-vinylimidazole-co-sodium styrenesulfonate); Hydrogels; Swelling; Ionic crosslink; Polyampholitic gel; Solvent effect; Colloidal gel; Ion pair production; Styrenesulfonate copolymer; Imidazole(vinyl) copolymer; Polyampholyte; Property composition relationship; Ionic strength; Proton transfer; Experimental study
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/S0014-3057(01)00159-8

Hydrogels of N-vinylimidazole (VI) and sodium styrenesulfonate (SSS) were synthesized by radical crosslinking copolymerization. Contrary to expectation, for some SSS compositions, the equilibrium swelling ( S eq) in deionized water shows a minimum with values close to those of collapsed states. In aqueous solutions of NaCl, S eq either remains constant, increases, or decreases with changes of the ionic strength, depending on the gel composition. These peculiarities are interpreted in terms of a sodium–proton exchange followed by the interaction of sulfonate groups with neighboring protonated imidazole rings, which behave as ionic crosslinks. The crosslink density due to ionic interactions was determined, as a function of composition, in deionized water, in methanol, and in 0.2 N NaCl aqueous solution.