Composition dependence of glass transition temperature of sulfonated‐polystrene ionomers

The glass transition temperatures of alkali (Na, K, Rb, Cs) and alkaline‐earth (Ba, Sr, Ca, Mg) ionomers of sulfonated polystyrenes (PSSA) with 3.4, 6.9, 12.7, and 16.7% of the styrene moieties sulfonated are reported. For the alkali‐metal PSSA ionomers, Tg depends on the degree of sulfonation, at least up to 13%, but not strongly on the nature of the cation. For the alkaline‐earth analogs Tg does not depend strongly on either the cation or the degree of sulfonation until the 16.7% level is reached. These and other reported data are discussed in terms of the role of cations in determining morphology.