High-performance anion exchange membranes based on poly(p-terphenylene quinuclidinium) with piperidinium side chains for fuel cells

Poly(p-terphenylene quinuclidinium) anion exchange membranes (AEMs) have remarkable chemical stability. However, their application in anion exchange membrane fuel cells (AEMFCs) is limited by the low conductivity resulting from poor ion mobility. In this study, novel poly(p-terphenylene quinuclidinium) polymers grafted with piperidinium suspended at the end of a long flexible alkyl side-chain are designed to prepare AEMs with both high conductivity and stability. The microphase separation morphology can be optimized by modulating the length of the flexible piperidinium side chains. Quaternary ammonium poly(p-terphenylene quinuclidinium) grafted with (6-bromoalkyl)-1-methylpiperidine (QPPTQ-6-Pip) has the most pronounced microphase separation structure, with higher water uptake (110.7 %), and thus the highest conductivity (194.7 mS cm −1 ) at 80 °C. Multi-carbon quinuclidinium's hydrophobicity suppresses swelling (48.4 %, 80 °C), which in combination with the microphase separation results in excellent alkaline stability of the membrane (retained 91.6 % at 80 °C after 1680 h immersion in 1 M NaOH). In addition, the side-chain length modulation enables QPPTQ-6-Pip to have excellent mechanical properties (tensile strength: 52.8 MPa, elongation at break: 21.5 %), thus allowing for application in fuel cells. The single cell test show that the peak power density is able to reach 1.24 W cm −2 , and the performance decays by 13.9 % after 90 h. This study provides an effective strategy to regulate the microstructure and performance of AEMs by grafting side chain engineering, which is of great significance to promote the practical application of high performance AEMs.