Design, synthesis and characterization of SEBS anion exchange membranes with ultrahigh dimensional stability

Poly(styrene-b-(ethylene-co-butylene)-b-styrene) copolymer (SEBS) has been widely used for anion exchange membranes (AEMs). However, it is still challenging to improve the dimensional stability of SEBS based AEMs because their main component poly(ethylene-co-butylene) phase (PEB) is rubbery. To this end, chemical crosslinking is widely built within the polystyrene phase (PS), but which still makes the PEB phase contribute nothing to the dimensional stability and ionic conductivity. Herein, we attempt to synthesize poly(styrene-b-butadiene-b-styrene) copolymers (SBS) owning adjustable content of 1,4-butadiene units via living anionic polymerization, following with hydrogenation. As more 1,4-butadiene units are copolymerized into SBS, the PEB phase becomes even harder, which significantly enhances the comprehensive performance of AEMs. The AEMs intentionally maximized by this approach not only have ultrahigh dimensional stability (i.e. 23.2 ± 0.1 of WU, 3.8 ± 0.1 of SR at 30 °C, nearly no change within 30 ~ 80 oC), but also exhibit a comparable hydroxide conductivity (~ 85 mS cm−1 at 80 °C with IEC as 1.06 ± 0.05 mmol/g). The membrane electrode assembly made from such AEM has a peak power density 370 mW cm−2 at a current density of 800 mA cm−2. This work provides a straightforward approach for fabricating long term alkaline durable and mechanically stable SEBS based AEMs, suitable for fuel cells application.