Anion Exchange Membranes by Cross-Linking Poly(styrene-<i>b</i>-ethylene-<i>co</i>-butylene-<i>b</i>-styrene) with Poly(aryl piperidinium) Containing Rigid-Flexible Units

With the increasing significance of green hydrogen production, anion exchange membrane-based water electrolysis (AEMWE) is gaining prominence. AEMWE with remarkable cell performance and durability has recently been developed, especially that built on poly(aryl piperidinium) (PAP)-based anion exchange membranes due to its high ion conductivity, remarkable chemical stability, and improved mechanical durability. In this work, we developed PAP-based cross-linked poly[(PPBP-co-pTP)-SEBS] membranes by chemically cross-linking two polymer components: a copolymer of para-terphenyl (pTP) and bis-4,4′-(3-phenylpropyl)biphenyl (PPBP), referred to as PPBP-pTP, and poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS). Specifically, the structurally rigid pTP was copolymerized with PPBP, containing flexible alkyl chains, forming a unit (PPBP-pTP) similar in structure to SEBS (a polymer combining the rigidity of styrene with the elasticity of ethylene–butylene). Subsequently, cross-linking PPBP-pTP and SEBS yielded x-(PPBP-pTP)-SEBS membranes with pronounced microphase separation. Additionally, x-(PPBP-15-pTP)-SEBS, with the 15% of PPBP content, exhibited the high OH– conductivity (126.71 mS/cm at 80 °C); excellent mechanical properties (tensile strength = 24.91 MPa and elongation at break = 57.59%); exceptional alkaline stability (100% conductivity retention in 2 M KOH at 80 °C after 960 h); and an excellent AEMWE cell performance of 2.67 A/cm2 at 1.8 V, using a non-noble catalyst for Ni-based oxygen evolution reaction applications.