Proton magnetic resonance studies of ionic solvation in ion-exchange resins.: Part I. Sulfonated cation-exchange resins

The proton magnetic resonance spectra of cation-exchange resins of crosslinkage X1 to X16 in the H+, Li+, Na+, K +, Rb+, Cs+, and NH4+ forms have been recorded and the values of the molal chemical shift, δM+0, are found to be −0.321, −0.005, 0.041, 0.031, 0.028, 0.015, and 0.00 (assumed) p.p.m./mole, respectively, for the cations. These values are very nearly equal to those observed in corresponding aqueous solutions, indicating that ion–solvent interactions are similar in both the resin matrix and the aqueous solution. The temperature dependence of the chemical shift shows the same trend. The effective hydration numbers calculated from the temperature dependence are 2.0 (4.81 m) for the H+ form, 4.8 (3.25 m) and 3.6 (5.26 m) for the Na+ form, 4.4 (3.9 m) for the K+ form, and 2.4 (6.18 m) for the Cs+ form. The ions in the resin phase behave as solutions of strong electrolyte, which is consistent with the polyelectrolyte gel model for the ion-exchange resin.