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

ABSTRACT 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.