Synthesis and Characterization of Sulfonated Co-Polyimides With Enhanced Flexibility, Thermal and Methanol Stability for Potential Fuel Cell Applications

Fabrication of proton exchange membranes with high conductivity, flexibility, and lower swelling ratio has been a lasting challenge. Here, we proposed a synthesis of highly flexible new sulfonated co-polyimides (co-SPIs) through one-step thermal imidization by polymerizing 4,4′-diaminostilbene-2,2′-disulfonic acid (SDA) with pyromellitic dianhydride (PMDA) and poly (ether amine) (PEA). Co-SPIs with a high degree of sulfonation (DS) (50%–70%) were successfully synthesized. These synthesized co-SPIs displayed good flexibility and thermal stability in comparison to literature-reported polymers. Furthermore, the methanol uptake for co-SPIs with 70% DS was 12.5%, which is less than standard Nafion (22% methanol uptake). Hence, these co-SPIs with enhanced flexibility, thermal stability, and lower swelling ratio in methanol make them a good candidate for fuel cell applications.