Effect of sodium salts on diffusion of poly(vinyl alcohol) in aqueous solutions

Abstract

The Taylor dispersion technique has been used for measuring the tracer diffusion coefficients, D0 Tracer, for poly (vinyl alcohol) (PVA) in aqueous systems containing two specific electrolytes (i.e., NaCl and Na2SO4) at three different concentrations (0.020, 0.050 and 0.10 mol dm−3), and at 25 °C. The selection of these salts has been based on the Hofmeister series of cations and anions, which order the ions with respect to the behavior of some macroscopic properties (such as, surface tension) and that can be interpreted as an effect salting-out or salting-in, depending if the target ions are strongly (kosmotropic) or a weakly hydrated (chaotropic). In this work, we have been used the combination of two kosmotropic ions (Na2SO4) and another one with a kosmotropic cation and a chaotropic anion (NaCl). These data, complemented by NMR measurements, permit us to have a better understanding about the effect of these sodium salts on transport and thermodynamic behaviour of PVA.