ABSTRACT
Abstract-Highly sulfonated poly(arylenethioethersulfone)s (SPTES) in a wide range of compositions and with bulky organic endgroups were synthesized from 3,3'-disulfonated-4,4'- difluorodiphenylsulfone (or the corresponding dichloro monomer), 4,4'-difluorodiphenylsulfone and 4,4'-thiobisbenzenethiol via a base-catalyzed nucleophilic displacement reaction in polar aprotic solvents. All the polymers were of high molecular weight, as evidenced by solution viscosity and GPC measurements, and could be solvent cast into tough, ductile, free-standing films for the measurement of proton conductivity. The proton conductivities of the proton-exchange membranes (PEMs), evaluated by a standard four-electrode measurement setup, ranged from 100 mS/cm to 300 mS/cm for the composition ranging from SPTES-50 to SPTES-100. The proton conductivities of the SPTES polymers correlated very well with their ion-exchange capacity (IEC) and water uptake. The SPTES polymer membranes were investigated, the results indicated that the SPTES polymers have excellent membrane-forming capability, as well as mechanical properties. A preliminary comparison of the performances of membrane electrode assemblies (MEAs) fabricated from SPTES-50 membrane and cast Nafion-117 membrane, at 80oC and 55% relative humidity, demonstrated that a peak power density twice that of Nafion-117 was obtained for the SPTES polymer membrane (0.34 W/cm2 at 0.6 A/cm2 for the SPTES membrane and 0.17 W/cm2 at 0.4 A/cm2 for Nafion-117).
