Ionic sulfonate groups were incorporated onto molecules of the rigid-rod polymer poly(p-phenylene terephthalamide) (PPTA) in two different positions. In one type, S-PPTA, ionic sulfonate groups were attached to the phenylene ring of the backbone chain. S-PPTA solubility was achieved in dimethylsulfoxide (DMSO) when 50% of the repeat units contained an ionic group. In the second type, PPTA-PS, where ionic propanesulfonate groups served as side chains, solubility was achieved in DMSO when 30% of the repeat units contained the ionic group. For both of the partially sulfonated ionic polymers, the thermal stability was enhanced in comparison with the stability of the acid-form polymers, but it was less than that of PPTA. The effect was more dramatic when the ionic groups were located at the end of side chains. The nature of the counterion also played a role, with doubly ionized calcium giving the best results. Polarized light micrographs of the ionic PPTA polymers displaced birefringent patterns and indicated that greater rigidity was present when the ionic groups were directly attached to the backbone, rather than at the end of a short side chain.