Cross-Linked Anion-Exchange Membranes with Dipole-Containing Cross-Linkers Based on Poly(terphenyl isatin piperidinium) Copolymers

Abstract

To balance the ionic conductivity and dimensional stability of anion-exchange membranes (AEMs), several cross-linked ether-free poly­(terphenyl isatin piperidinium) copolymers were synthesized using 1,2-bis­(2-aminoethoxy)­ethane as a cross-linker. By introducing an alkyl diamine-based hydrophobic cross-linker as a control, the effects of the dipolar-molecule-containing cross-linker on the comprehensive performance of the membranes were investigated. Cation–dipole interactions between the cations and the hydrophilic ethylene oxide cross-linker enhance the self-assembly capability of the cationic groups. The introduction of the rotatable ethylene oxide cross-linker facilitates the flexibility of the cross-linked networks, thereby promoting hydrophilic/hydrophobic phase separation and inhibiting excessive swelling of the corresponding AEMs simultaneously. The resulting PTPBHIN-O19 membrane showed a high hydroxide conductivity (151.69 mS cm–1) and low swelling ratio (10.53%) at 80 °C. Furthermore, owing to the cross-linked structure and ether-free polymer backbone with high alkali resistance, the membranes treated in 3 M NaOH at 80 °C for 1600 h maintained ≥85% of their hydroxide conductivity, indicating excellent alkaline stability. A H2/O2 fuel cell based on the PTPBHIN-O19 AEM exhibited a maximum power density of 398 mW cm–2 at 515 mA cm–2.

Enhancing the Chemical Stability of Poly(isatin terphenyl)-Based Anion Exchange Membranes by Cross-Linking with Quaternary Ammonium-Functionalized Noria

“…Table displays the physicochemical properties of the proposed membrane and other recently reported AEMs. Compared to the AEMs having the similar structures of poly­(isatin terphenyl) but without the macrocyclic cross-linker, ,− the proposed QPIBT-4.3%FNoria membrane shows superior comprehensive properties including competitive conductivity and excellent chemical stability. This membrane endows the single fuel cell to achieve an obviously high peak power density ( P max ) and acceptable durability.…”

Current Challenges on the Alkaline Stability of Anion Exchange Membranes for Fuel Cells

“…Notably, the H 2 /O 2 single fuel cell with this piperidinium‐based AEM realized a power density of up to 661 mW cm −2 . Recently, novel AEMs prepared using superacid‐catalyzed biphenyl and N‐methylpiperidone have received attention [71,72] . Because the piperidinium structure is easy to prepare and exhibits excellent alkaline stability, piperidinium groups are advantageous for introduction into AEMs.…”

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

“…The introduction of long flexible alkyl side chains on polyfluorene can effectively improve its solubility in conventional organic solvent. − However, the harsh reaction conditions required for this transformation limit their commercial application. Recently, superacid-catalyzed Friedel–Crafts polycondensation has been used to obtain ether-free aromatic polymers under relatively mild reaction conditions. − The obtained aromatic-polymer-based PEMs show good mechanical, dimensional, and chemical stability. − …”