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, T_g 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 T_g 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.