Volumetric Study of the Interaction Between Chloride Salts and Polyvinylpyrrolidone in Aqueous Solution

We are interested in polyvinylpyrrolidone as an analog for the D-state proteins. In a volumetric study, the interactions between polyvinylpyrrolidone (PVP) and sodium-, potassium-, calcium-, and tetrabutylammonium chloride at 35°C in a series of aqueous PVP solutions over a concentration range of PVP up to 20 wt.% was performed. The volumes of transfer at infinite dilution _trV₂⁰ from water to the PVP solutions were determined for the salts; their decreasing order showed a parallel relation to the Hoffmeister series. The _trV₂⁰ data were analyzed by applying the McMillan–Mayer method to obtain the volumetric interaction coefficients between the ions and the polymer unit.