Preparation and thermal characterization of the glass transition temperatures of sulfonated polystyrene-metal ionomers

The glass transition temperatures and heat capacity changes in the transition region are reported for six sulfonated linear polystyrenes in the hydrogen form, H‐SPS, in the 3.4–20.1 mol % sulfonation range and 76 metal SPS ionomers in the 3.4–12.8 mol % range. The metals are those which interact predominantly ionically and include +1, +2, and +3 ions of the alkali metal, alkaline earth, and rare earth (lanthanide) series. The results show the effect of H2O or coordinating ligands on glass transition temperatures (Tg) and the importance of eliminating it to obtaining reproducible values for Tg and ΔCp. The Tg values of dry M‐SPS ionomers depend only on the sulfonation level despite wide variation in metal ion charge and size. The variation of ΔCp with sulfonation level is interpreted as showing that at high levels a few unsulfonated styrene units adjacent to sulfonated ones are constrained, presumably by clustering, from participation in the polystyrene‐like cooperative rearrangements in the transition region.