Cationic Metallo‐Polyelectrolytes for Robust Alkaline Anion‐Exchange Membranes

Abstract

Chemically inert, mechanically tough, cationic metallo‐polyelectrolytes were conceptualized and designed as durable anion‐exchange membranes (AEMs). Ring‐opening metathesis polymerization (ROMP) of cobaltocenium‐containing cyclooctene with triazole as the only linker group, followed by backbone hydrogenation, led to a new class of AEMs with a polyethylene‐like framework and alkaline‐stable cobaltocenium cation for ion transport. These AEMs exhibited excellent thermal, chemical and mechanical stability, as well as high ion conductivity.

Metallo-polyelectrolytes as a class of ionic macromolecules for functional materials

“…For example, cationic Ru complexes exhibited excellent stability in NaOH solution at room temperature over six months 23 . Similarly, no significant changes were observed for cobaltocenium cyclooctene monomer in 1 M NaOH solution at 80 °C for two weeks 24 . Only 7% of dimethyl cobaltocenium cation degraded after storing in 1 M KOH at 80 °C for 30 days 150 .…”

“…Permethyl cobaltocenium cation showed a much longer lifetime than many other organic cations under high temperature (only 8.5% degraded at 140 °C in 1 M NaOD/D 2 O after 6 weeks) 151 . In addition, both mono-substituted and permethyl cobaltocenium-containing polyelectrolytes showed excellent thermal stability with decomposition temperature over 300 °C, which is significantly higher than most ammonium or imidazole-functionalized polyelectrolytes 24 , 151 . However, more rigorous tests are required to reveal the stability of these metal complexes under highly basic and also highly oxidative conditions, especially at the device level 152 .…”

“…This property could open up many new applications for metallo-polyelectrolytes beyond traditional organo-polyelectrolytes 8 , 22 . In addition, metal cations may exhibit significantly distinct behaviors in thermal and chemical stability for some applications 23 , 24 . On the other hand, metals are generally used as cationic centers for building polyelectrolytes, thus it is fair to compare metallo-polyelectrolytes with cationic organo-polyelectrolytes, particularly the most studied quaternary ammonium-based counterparts.…”

Recent development in polyolefin-based anion exchange membrane for fuel cell application

“…膜中的BTMA基团受到氢氧根离子的进攻, 生成苄 醇结构, 使得离子交换容量下降 [33] . 为了进一步提 图 6 (网络版彩色)聚烯烃类阴离子交换膜的碱性稳定性 Figure 6 (Color online) Alkaline stability of AEMs based on polyolefins 高碱性稳定性, 本课题组 [24] 制备了侧链型聚烯烃阴 [21] 、二茂钴阳离子 [22] 、位阻型咪唑盐 [20] 、和吡咯 盐 [27] , 分别引入聚烯烃阴离子交换膜中, 得到高碱 性稳定性的膜材料. 例如, 含有稳定的位阻型季鏻盐 和金属离子的AAEM-17 [21] 和H-AEM 50 -OH [22] 的聚烯 烃类阴离子交换膜具有较高的碱性稳定性, 能够在1 mol/L NaOH和80℃的条件下, 分别稳定22 d和1个月.…”

Cross‐Linked Spirocyclic Quaternary Ammonium‐Based Anion Exchange Membrane with Tunable Properties for Fuel Cell Applications

“…In the past few years, variety aromatic polymers with pendent quaternary ammonium cations, such as poly(styrene)s, poly(sulfone)s, poly(phenylene oxide)s, poly(arylene ether)s, poly(phenylene)s, polypropylene and poly(olefin)s, have been used in the preparation of AEMs . However, quaternary ammonium cations are unstable in alkaline environment due to the Hofmann degradation,, the nucleophilic substitution and the ylide reaction . Therefore, various types of AEMs based on some potential alternative cations, including imidazolium,, guanidinium, phosphonium, metal‐cation, pyridinium, tertiary sulfonium and pyrrolidinium cations have been prepared and investigated.…”