Solution Properties of Polystyrene-Based Ionomers in Polar and Low-Polarity Solvents

Abstract

We studied various factors that influenced the solution properties of polystyrene-based ionomers. Factors studied were: (1) counterion, (2)ion-content, and (3) added salt. With respect to the counterion effect, it was found that the order of counterion binding of ionomers in a polar solvent was the same as the order of aggregation in a low-polarity solvent for the same ionomer. It was also found that the order of these effects for a carboxylated ionomer was opposite to that for a sulfonated ionomer. With respect to the ion-content effect, it was shown that both polyelectrolyte behavior and aggregation behavior were enhanced with increasing ion-content. In a polar solvent, the effective diameter of ionomers increased with ion-content, at least up to the 5 mole % level. In a low-polarity solvent, the second virial coefficient decreased with increasing ion-content, because the excluded volume effect of styrene was compensated by the attractive interaction between ion-pairs. With respect to the added salt effect, it was shown that both polyelectrolyte behavior and aggregation behavior were suppressed by added salts.