I-127 AND K-39 NMR-STUDY OF THE INTERACTION OF IONS WITH WATER-SOLUBLE POLYMERS

Thermodynamic parameters including the equilibrium constant for the binding of iodide anion with polymers in aqueous solutions have been determined from the excess line widths of the127 I NMR. Comparison of these parameters with the NMR line widths suggests that a specific binding exists to cause severe line broading of the127I NMR in solutions of poly(vinylpyrrolidone) (PVP), isotactic poly(2-hydroxyethyl methacrylate), and poly(acrylamide). Even in the absence of significant polymer-iodide binding, the asymmetric hydration of iodide anions in the solutions of poly(ethylene oxide) and poly(vinyl alcohol) seems to cause moderate line broadening. The magnitude of the binding constant of iodide anions can be related to the dipole moment of the polymer segment, which suggests that an electrostatic interaction is responsible for the specific iodide binding with PVP. The127I NMR line widths obtained with different alkali ions and the39K NMR data indicate no effects of countercation on the127I NMR. © 1990, American Chemical Society. All rights reserved.