Raman spectroscopic studies of acid dissociation in sulfonated polystyreneresins

FT-Raman spectra of sulfonated polystyrene resins with varying levels of su lfonation from 9-97% have been recorded. Molecular markers of -SO3H and -SO 3- moieties have been proposed and used to determine quantitatively the deg ree of dissociation of the acids as a function of total sulfonic acid and s ulfonate concentrations. Comparison with the ethanesulfonic acid/water syst em has been made and it is concluded that the low-sulfonation and high-sulf onation resins closely resemble this molecular acid/water system, but that intermediate sulfonation specimens are dissociated some 18% less than the c orresponding ethanesulfonic acid/water analogues. This is ascribed to the p resence of hydrogen-bonded acid groups with water in the gel region of the resins which had been suggested in previous infrared spectroscopic measurem ents. (C) 2001 Elsevier Science BN. All rights reserved.