Poly(fluorenyl terphenyl piperidinium) with Sulfonated Side Chains for the Application of High-Temperature Proton Exchange Membranes

To produce proton exchange membranes (PEMs) with robust mechanical properties, poly(fluorenyl terphenyl piperidinium) (PFTP) with an aromatic backbone is synthesized. Sulfonated PFTP (SPFTP- x ) is obtained by introducing propanesulfonic acid onto PFTP as a side chain to enhance its phosphoric acid (PA) adsorption capacity and proton conductivity. Both the PFTP and SPFTP- x membranes exhibit good thermal, oxidization, and dimensional stabilities owing to their rigid ether-free aromatic backbones. Because of the introduction of propanesulfonic acid side chains, the SPFTP- x membranes show higher PA adsorption capacity and higher proton conductivity than the PFTP membrane. The PA doping content of the SPFTP- x membranes is more than 160% at room temperature, and their conductivity can be up to 109.0 mS cm –1 at 160 °C under anhydrous condition. Furthermore, a single cell assembled with SPFTP-50 exhibits a maximum power density of 280 mW cm –2 at 100 °C. These results indicate that SPFTP- x is a promising membrane material for applications in high-temperature proton exchange membrane fuel cells.