Abstract
In this work, the thermodynamic properties of aqueous solutions of sulphopropylic derivatives of polyvinyl alcohol with various DS (PVS) are studied and compared with those of polyethylenesulphonic acid and carboxymethylcelluloses (CMC). The fractions of free monovalent and divalent counter-ions are measured by potentiometry and conductimetry; the values are compared with the theoretical values calculated by an electrostatic treatment previously proposed. The experimental values are always lower than those obtained with CMC; this effect is attributed to the flexibility of vinyl backbone ( b eff/ b struct = 0·775). By potentiometry, the selectivity is established as Cs + > K + > Na + > Li + analogous to that of sulphonic resins for PES; on PVS there is no selectivity between monovalent counter ions. Exchange energy ΔG K Ca is determined as function of DS but the values are always lower than with CMC, showing the influence of the chemical characteristic of the ionic sites on the exchange mechanism.
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