digilib@itb.ac.id +62 812 2508 8800

A series of high polymer content phosphoric acid-dopedm/p-polybenzimidazole (PBI) copolymer membranes were prepared via the poly(phosphoricacid) (PPA) process. These copolymer membranes showed much higher solubility insolution (7?10 wt %) compared to the homopolymerpara-PBI (typically <3.5 wt %),which translated to higher polymer solids content in the PPA-processed dopedmembranes. Concurrent with these changes, the compressive creep compliance (J)decreased from approximately 1×10?5to <2×10?6Pa?1. These membranes exhibitedhigh proton conductivities, >150 mS/cm at typical operating temperatures of 160?200°C, and showed exceptional low voltage decay,?0.67?V/h when tested at 160°C formore than 2 years.