Physically Self-Cross-Linked SEBS Anion Exchange Membranes

Two kinds of commercially available poly(styrene-b-butadiene-b-styrene) copolymers (SBS1301 and SBS1401) with 86-87% of 1,4-butadiene units were modified to fabricate robust poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) anion exchange membranes (AEMs) via sequential hydrogenation, chloromethylation, quaternization, and alkalization. Its poly(ethyleneco-butylene) phase could provide a physically self-cross-linked structure responsible for the mechanical stability of AEMs, due to the crystalline behavior (T-m = similar to 80 degrees C and similar to 20% of crystallinity) of polyethylene segments after the hydrogenation of 1,4-butadiene units. The polystyrene phase was liberated from the chemical cross-linking structures to focus on conducting ion transport. Different from commercial SEBS based AEMs, this specially designed microphase separation structure led to low swelling ratio, high water uptake, and good hydroxide conductivity (e.g., similar to 12%, similar to 80%, similar to 81 mS cm(-1) at 80 degrees C) at moderate ion exchange capacity (IEC = 1.48 mmol g(-1) ) for the SEBS1401-OH AEMs made from SBS1401. The single cell using SEBS1401-0H has a peak power density as high as 320 mW cm(-2) while the current density achieves 860 mA cm(-2) . These results indicate that the proposed method can develop high-performance SEBS based AEMs, suitable for fuel cell applications.