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

Barbora Filova,Barbora Filova,Lenka Musilova,Ana C.F Ribeiro,M Luísa Ramos,Aleš Mracek,Artur J.M Valente,Luis M.P Veríssimo

doi:10.1016/j.molliq.2020.112728

Barbora Filova, Barbora Filova + Show 6 more

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https://doi.org/10.1016/j.molliq.2020.112728

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Abstract

Abstract The Taylor dispersion technique has been used for measuring the tracer diffusion coefficients, D0Tracer, 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.

Highlights

Poly(vinyl alcohol) (PVA) is a polymer of great interest because of its many desirable characteristics for a wide range of applications, including pharmaceutical, biomedical, electrochemistry [1], and sensors [2,3]
We proposed an experimental study of the binary diffusion for systems containing water and PVA over the concentration range from (0.001 to 0.227) mol dm−3, by using Taylor's dispersion technique at 25 °C
As a first approach we aim to understand if the presence of ions, in particular sulfate and chloride, in solution would affect the structure of PVA

Summary

Introduction

Poly(vinyl alcohol) (PVA) is a polymer of great interest because of its many desirable characteristics for a wide range of applications, including pharmaceutical, biomedical, electrochemistry (for example, super-capacitors) [1], and sensors [2,3]. PVA has a relatively simple chemical structure with a pendant hydroxyl group (Fig. 1a). The monomer, vinyl alcohol, does not exist in a stable form, rearranging to its tautomer, acetaldehyde. PVA is produced by the polymerization of vinyl acetate to poly(vinyl acetate) (PVAc) followed by the hydrolysis to PVA (Fig. 1b). Once the hydrolysis reaction is not complete, there are PVA with different degrees of hydrolysis (Fig. 1b). PVA is always a co-polymer of vinyl alcohol and vinyl acetate [4]

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