ANION BINDING-PROPERTIES OF POLY(VINYLPYRROLIDONE) IN AQUEOUS-SOLUTION STUDIED BY HALIDE NMR-SPECTROSCOPY

Abstract

Interaction between halide ions and poly(vinylpyrrolidone) (PVP) in aqueous solution has been shown to cause significant line broadening in Cl-35, Br-81, and I-127 NMR. This excess NMR line width has been used to obtain the intrinsic binding constants of Cl-, Br-, and I- with PVP. Other anionic species in the aqueous halide-PVP solution have been found to compete with the halide for binding to the polymer, resulting in a decrease of the excess halide NMR line width. Such competition between the halide and other anion has been used to obtain the intrinsic binding constants of various other anions. The binding constants follow the sequence SO4(2-) < F- < Cl- < NO3- < Br- < I- < SCN-, which is nearly identical with the lyotropic series. This binding affinity correlates with the polarizability of anions.