High performance anion exchange membranes obtained through graft architecture and rational cross-linking

• Br-PPO was used for the preparation of graft copolymers.
• The cross-linked AEMs were prepared with well-defined ionic channels.
• The AEMs achieved high hydroxide conductivity, dimensional/chemical stability.

The graft copolymers poly(phenylene oxide)-g-quaternary 4-vinylbenzyl chloride (PPO-g-Q) with varied graft ratios ranging from 72% to 115% were synthesized according to the previous work. The resulting membranes displayed high hydroxide conductivity, while other fuel cell related properties are not so excellent. To enhance dimensional, thermal and alkaline stability of the PPO-g-Q anion exchange membranes (AEMs), brominated poly(phenylene oxide) (Br-PPO) possessing the identical compositions with the hydrophobic backbone of the graft copolymers, was used as a macromolecular cross-linker to form cross-linked networks in the hydrophobic domains. The simultaneous improvements of conductivity and stability were achieved with the combination of unique graft architecture and rationally designed cross-linking. Among these AEMs, Cr-PPO-g-Q115 presented a high hydroxide conductivity of 128 mS/cm at 90 oC, a low dimensional swelling of 6.0%, and a dramatically improved thermal and alkaline stability compared with the uncross-linked membranes. The outstanding properties indicated the promising application of Cr-PPO-g-Q in fuel cells.

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