End-crosslinked block copolymer with methyl morpholinium and anion exchange membrane using the same

Methyl Morpholinium Anion Exchange Membrane with Reduced Conductivity Loss via Azide End-Crosslinking

This technology features a polymer membrane based on a poly(arylene ether sulfone) multiblock copolymer (MM-PES) with methyl morpholinium as the conductive group, crosslinked exclusively at the polymer chain ends using an azide compound. It is engineered to achieve a tensile strength of 51 MPa and long-term high-temperature durability with a hydrophilic composition ratio of 1.5:1 and 15 wt% crosslinker.

While anion exchange membranes enable the use of non-precious metal catalysts in alkaline fuel cells, they have historically suffered from significantly reduced stability in highly alkaline environments above 80°C. Conventional crosslinking methods used to improve stability have had the drawback of reducing ion conductivity due to the formation of rigid 3D networks and decreased water uptake.

This technology limits crosslinking to the chain ends to minimize 3D network formation, while leveraging the steric structure of bulky morpholinium cations to ensure both OH- conductivity and alkaline stability. The membrane can be fabricated simply by heat-treating the solution-cast film at 180°C. It maintains conductivity under partially humidified conditions by reducing water uptake while enhancing water retention. Applicable to anion exchange membranes for alkaline fuel cells and water treatment membranes like electrodialysis and water purification filters, it effectively slows performance degradation during long-term high-temperature operation.

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Key Features:

• End-crosslinked polymer membrane where methyl morpholinium-functionalized poly(arylene ether sulfone) multiblock copolymer is crosslinked by an azide compound crosslinker
• Configuration where crosslinking is introduced only at the ends of the MM-PES polymer chain with a high-hydrophilic composition of 1.5:1 (n:m)
• Polymer membrane achieving 51 MPa tensile strength and maintaining appearance and flexibility after 500 hours at 80°C using 15 wt% azide crosslinker relative to MM-PES weight
• Process of mixing MM-PES and azide crosslinker in DMF solvent, casting into a film, drying, and crosslinking via heat treatment at 180°C

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This invention was developed with support from the Ministry of Science, ICT and Future Planning for the development of high-performance anion exchange membrane source materials through molecular structure control.

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