A series of isoprene and sodium styrene sulfonate copolymers (poly(I-co-NaSS)) was synthesized with systematically varied concentrations of ions using radical emulsion polymerization. Their chemical structures and morphologies were characterized and structure-mechanical relationships were determined. The SAXS scattering profiles and the thermal properties remained unchanged as ion content increased. In contrast, the toughness and stiffness of the copolymers increased and the adhesion strength was significantly improved as the ion content increased from 1.2 mol % to 4.6 mol % NaSS.