Sulfonated Poly(Phenylene Sulfone)s Ionomers

SPPSU(2S) and SPPSU(4S) ionomers with two and four sulfonic acid groups per PPSU unit were synthesized and characterized. SPPSU(2S) ionomers were synthesized and characterized by varying the acid type, sulfonation temperature, and time. Mild sulfuric acid was suitable for sulfonation of PPSU(2S). The IEC, molecular weight, and viscosity of SPPSU(2S) ionomers were 3.42–5.15 meq/g, 150,000–430,000, and 50–80 mPa·s, respectively, depending on the synthesis conditions. The tensile strength of SPPSU(2S) ionomer membranes was higher than that of Nafion membrane, the tensile elongation was lower than that of Nafion membrane, and the elastic modulus was higher than that of Nafion membrane. The conductivity of SPPSU(2S) ionomer membranes was similar to that of Nafion212 membrane. On the other hand, SPPSU(4S) ionomer was synthesized by monomers. The IEC and molecular weight of SPPSU(4S) ionomer were 5.6 meq/g and 303,203. The viscosity of SPPSU(4S) ionomer was higher than that of SPPSU(2S) ionomer. The stress-strain properties of SPPSU(4S) ionomer membrane showed a slightly higher elastic modulus than Nafion membrane, but the tensile strength and tensile elongation were similar to those of Nafion membrane. In addition, the conductivity of SPPSU(4S) ionomer membrane was higher than that of SPPSU(2S) and Nafion membranes. The above characteristics of SPPSU(2S) and SPPSU(4S) ionomer membranes are expected to be used as ionomer electrolytes for energy devices.