Dynamics of Sodium Ions and Water in Swollen Superabsorbent Hydrogels as Studied by 23Na‐ and 1H‐NMR. Issue 2 (22nd November 2018)

• Record Type: Journal Article
• Authors: Guo, Xiaoai; Theissen, Solveig; Claussen, Jan; Hildebrand, Viet; Kamphus, Juliane; Wilhelm, Manfred; Luy, Burkhard; Guthausen, Gisela
• Is Part Of: Macromolecular chemistry and physics. Volume 220:Issue 2(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-11-22
• Subjects: 23Na‐NMR -- hindered diffusion -- hydrogels -- pulsed field gradient NMR -- superabsorbent polymers; Polymers -- Periodicals; Polymerization -- Periodicals; Synthetic products -- Periodicals; Macromolecules -- Periodicals; 547.7
• DOI: 10.1002/macp.201800350
• Languages: English
• ISSNs: 1022-1352

Abstract

Abstract: Dynamics of sodium ions and water in swollen superabsorbent polymer (SAP) hydrogels are studied by 23 Na‐ and 1 H‐NMR, respectively. The apparent diffusion coefficients of water in swollen SAPs, probed by 1 H pulsed field gradient NMR, decreases with increasing diffusion time. The degree of hindrance depends on structural and synthesis parameters. It is quantified within a tortuosity model. Based on the results, the swelling degree has the highest impact on the ion mobility, apart from synthesis parameters leading to different levels of physical and chemical crosslinks. 23 Na‐NMR relaxation and diffusion reveal the 23 Na + mobility in swollen SAPs. A higher degree of neutralization leads to faster relaxation and to a smaller apparent diffusion coefficient. Surface crosslinking restricts water mobility, but has a smaller impact on the dynamics of sodium ions. The experimental results indicate an influence of SAP structure on the dynamics of ions and water molecules. Abstract : Dynamics of 23 Na + and water in swollen superabsorbent polymers (SAPs) are probed by 23 Na‐ and 1 H‐NMR, respectively. The steric hindrance of the SAP network on water mobility is quantified within a tortuosity model for the 1 H diffusion coefficient. 23 Na‐NMR relaxation and diffusion experiments reveal 23 Na + mobility in swollen SAPs. Their mutual interactions with hydrophilic networks are explored.