Quaternized triblock polymer anion exchange membranes with enhanced alkaline stability

Alkaline stability is the critical issue for the practical application of anion exchange membranes (AEMs) in fuel cells. The benzyltrimethyl ammonium and backbone with C-O linkages of the traditional AEMs are susceptible to attack by hydroxide ions resulting in poor alkaline stability of the AEMs. Herein, we present the preparation of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) triblock copolymer via grafting, ketone reduction and quaternization for AEM fuel cell applications. The quaternary ammonium (QA) groups are attached to the SEBS backbone free of C-O linkages via long flexible alkyl spacers, which are responsible for the robust alkaline stability of the AEMs. Thus, the hydroxide conductivity of SEBS-CH2-QA-1.5 was only decreased by 7.7% and 13.7% after immersing the membranes into a 1 M aqueous KOH solution at 60 and 90 degrees C for 360 h, respectively. Furthermore, SEBS-CH2-QA-1.5 with IEC of 1.23 meq g(-1) exhibits a maximum hydroxide conductivity of 56.4 mS cm(-1) at 80 degrees C and a maximum power density of 94.6 mW cm(-2) under a current density of 300 mA cm(-2).