Water Molecules’ and Lithium Cations’ Mobility in Sulfonated Polystyrene Studied by Nuclear Magnetic Resonanceстатья
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Дата последнего поиска статьи во внешних источниках: 20 февраля 2024 г.
Аннотация:The hydration of ions and charge groups controls electro mass transfer through ion exchangesystems. The self-diffusion and local mobility of water molecules as well as lithium cations inpoly (4-styrenesulfonic acid) and its lithium, sodium and cesium salts were investigated for the firsttime using pulsed-field gradient NMR (PFG NMR) and NMR relaxation techniques. The temperaturedependences of the water molecule and Li+cation self-diffusion coefficients exhibited increasingself-diffusion activation energy in temperature regions below 0C, which is not due to the freezing ofparts of the water. The self-diffusion coefficients of water molecules and lithium cations, as measuredusing PFG NMR, are in good agreement with the self-diffusion coefficients calculated based on Einstein’sequation using correlation times obtained from spin-lattice relaxation data. It was shown thatmacroscopic water molecules’ and lithium cations’ transfer is controlled by local particles jumpingbetween neighboring sulfonated groups. These results are similar to the behavior of water and cationsin sulfonic cation exchanger membranes and resins. It was concluded that polystyrenesulfonic acid isappropriate model of the ionogenic part of membranes based on this polymer.