Alkali-Stable Anion Exchange Membranes Based on Poly(xanthene)

Area of Science:

• Polymer Chemistry
• Materials Science
• Electrochemistry

Background:

• Anion exchange membranes (AEMs) are crucial for alkaline energy conversion devices.
• Developing AEMs with high ionic conductivity, thermal stability, and chemical resistance remains a challenge.

Purpose of the Study:

• To synthesize and characterize a novel class of poly(xanthene) (PX) based AEMs.
• To evaluate the performance of these PX AEMs in terms of ionic conductivity, thermal stability, and alkaline stability.

Main Methods:

• Synthesis of PX polymers via superacid-mediated polyhydroxyalkylation and subsequent quaternization.
• Characterization of AEM properties including ionic conductivity, thermal stability (thermogravimetry), and alkaline stability (NMR spectroscopy).

Main Results:

• PX AEMs with trimethylammonium, methylpiperidinium, and quinuclidinium cations were successfully prepared.
• Achieved high hydroxide conductivity up to 129 mS cm^-1 at 80 °C.
• Demonstrated excellent alkaline stability, with <4% ionic loss after 720 h in 2 M NaOH at 90 °C, maintaining backbone integrity.

Conclusions:

• The rigid PX backbone and flexible cation-bearing side chains contribute to high performance.
• PX AEMs are promising candidates for durable anion exchange membranes in alkaline fuel cells and electrolyzers.