Design and synthesis of poly(styrene-b-(ethylene-co-butadiene)-b-styrene) anion exchange membranes with high ion conductivity

Poly(styrene-b-(ethylene-co-butadiene)-b-styrene) copolymers (SEBS) have garnered significant attention to develop anion exchange membranes (AEMs) for fuel cells. However, SEBS commodities encounter a formidable obstacle of fabricating high-performance AEMs as thermoplastic elastomer. Herein, a series of poly(styrene-bbutadiene-b-styrene) copolymers (SBS) with high content of 1,4-butadiene units (>90 % of middle block) and variable content of polystyrene (PS, 51.3, 61.6 and 70.7 wt%) has been designed to develop SEBS AEMs with high-strength polyethylene phase via hydrogenation, chloromethylation, quaternization and alkalization. The results demonstrate that high PS content broadens the ion transport channel, improves the ion exchange capacity (IEC) and alkali resistance stability, and substantially boosts the ion conductivity, water uptake and swelling ratio of AEMs. Besides, the high proportion of polyethylene phase from 1,4-butadiene unit of SBS copolymers provides good dimensional stability to the AEMs. Remarkably, the AEMs with 70.7 wt% PS and an IEC value of 3.37 mmol g(-1) significantly upgrades the ionic conductivity to -190 mS cm(-1) at 80 degrees C. It attains a peak power density of -1000 mW cm(-2) at 2.09 A cm(-2) in a H-2/O-2 single cell operating at 80 degrees C. This outstanding performance underscores the promising potential of such SEBS copolymers in the development of high-performance SEBS AEMs for fuel cells.