NMR and density study of Co 2+ site binding by polyelectrolytes

Abstract

The changes of density and chemical shifts of the water proton upon addition of CoCl 2 to aqueous solutions of tetramethylammonium salts of seven polyelectrolytes (polyphosphate, maleic acid-methylvinylether alternated copolymer, polyacrylic acid, carboxymethylcellulose of substitution degree 0.98, 1.3, 2.1, 2.65) have been measured. Assuming a negligible contribution of pseudo-contact interaction to the water proton chemical shift and a constant hyperfine constant upon displacement of water molecules by other ligands, has permitted the calculation of (i) the number of water molecules released by Co 2+ ions upon binding and the approximate fraction of Co 2+ ions bound with loss of water, and (ii) the total volume change upon binding and the individual contributions of counterions and polyelectrolyte charged sites to this volume change. Our results are generally in agreement with those obtained using other methods.