Sulfonated poly(arylene ether) membranes containing perfluorocyclobutyl and ethynyl groups: Increased mechanical strength through chain extension and crosslinking

Novel extendable and crosslinkable sulfonated poly(arylene ether) copolymers (ESHQx-CMy) were synthesized. These copolymers utilized 4-[trifluorovinyl(oxy)]phenol (TFP) as a linker to extend the polymer and provide better elongation at break and mechanical strength. The extension moiety was successfully synthesized and introduced at the chain end of the sulfonated poly(arylene ether) copolymers to induce a strong interaction of the copolymer while maintaining its flexibility. The extension and crosslinking reactions were performed by thermal curing at 200°C, and confirmed by FT-IR and chemical resistance testing. The synthesized copolymers (ESHQx-CMy) possessed reasonable thermal and chemical stability. In addition, the elongation at break was improved to 14.2%, with a higher tensile strength (73.6MPa) than other sulfonated poly(arylene ether) copolymers containing only a crosslinked moiety (CM). Importantly, these novel copolymers also displayed the highest proton conductivity (0.145S/cm) than Nafion 212 (0.093S/cm) at room temperature. Novel polymer electrolyte membranes (ESHQx-CMy) were synthesized with the extensible and crosslinkable moieties for fuel cell application. The synthesized copolymers not only have strong interactions but also are flexible because of the extension of the polymer, displaying increased elongation at break (14.2%) and mechanical strength (73.6MPa). Therefore, the ESHQx-CMy membranes could have higher proton conductivity (0.145S/cm) than that of Nafion 212. [Display omitted] •Chain-extension moiety, 4-[trifluorovinyl(oxy)]phenol (TFP), was successfully synthesized and introduced at the end of the polymer.•Chain-extension displayed similar characteristics when compared with crosslinking with the additional trait of increasing molecular weight while having a flexible chain.•Extended and crosslinked polymer had better toughness with improved elongation at break and high tensile strength.•Synthesized polymer electrolyte membrane had higher proton conductivity (0.145S/cm) than that of Nafion 212 (0.093S/cm).