The Effect of Various Functional Groups on the Morphology and Performances of Crosslinked Addition-Type Poly(Norbornene)s-Based Anion Exchange Membranes

Abstract

To investigate the effect of different functional groups on the morphology and properties of crosslinked anion exchange membranes (AEMs), a series of novel partially crosslinked addition-type poly(norbornene)s-based AEMs were prepared by flexibly grafting N-methylpyrrolidinium, N-methylpiperidinium, N-methylmorpholinium, and 1, 2-dimethylimidazolium onto an addition-type poly(norbornene)s backbone. The well-developed microphase separation morphology was observed for all the prepared crosslinked AEMs using AFM and SAXS. The AEM with N-methylpyrrolidine groups (CL-aPNB-TMHDA-MPY) constructed more uniform and wider ion transport channel, exhibiting the highest hydroxide conductivity of 122.0 mS cm⁻¹ at 80°C. The AEM-tethering N-methylpiperidine cations (CL-aPNB-TMHDA-MPRD) exhibited the best alkaline stability and achieved 90.61% conductivity retention even after being soaked in 1 M NaOH at 80°C for 1008 h. Meanwhile, the order of alkaline stability was CL-aPNB-TMHDA-MPRD>CL-aPNB-TMHDA-MPY>CL-aPNB-TMHDA-DMMI>CL-aPNB-TMHDA-NMM. The peak power density of a H₂/O₂ fuel cell equipped with CL-aPNB-TMHDA-MPY, CL-aPNB-TMHDA-MPRD, CL-aPNB-TMHDA-NMM, and CL-aPNB-TMHDA-DMMI were 247.3, 218.1, 185.9, and 178.0 mW cm⁻² at 80°C, respectively. These results of the comparison of AEMs with different cation groups give some insights for designing high-performance AEMs in future.