Anion Exchange Membranes\nby Cross-Linking Poly(styrene‑<i>b</i>‑ethylene-<i>co</i>-butylene‑<i>b</i>‑styrene) with\nPoly(aryl piperidinium) Containing\nRigid-Flexible Units

With the increasing significance of green hydrogen production,\nanion exchange membrane-based water electrolysis (AEMWE) is gaining\nprominence. AEMWE with remarkable cell performance and durability\nhas recently been developed, especially that built on poly(aryl piperidinium)\n(PAP)-based anion exchange membranes due to its high ion conductivity,\nremarkable chemical stability, and improved mechanical durability.\nIn this work, we developed PAP-based cross-linked poly[(PPBP-<i>co</i>-pTP)-SEBS] membranes by chemically cross-linking two\npolymer components: a copolymer of <i>para</i>-terphenyl\n(pTP) and bis-4,4′-(3-phenylpropyl)biphenyl (PPBP), referred\nto as PPBP-pTP, and poly(styrene-<i>b</i>-ethylene-<i>co</i>-butylene-<i>b</i>-styrene) (SEBS). Specifically,\nthe structurally rigid pTP was copolymerized with PPBP, containing\nflexible alkyl chains, forming a unit (PPBP-pTP) similar in structure\nto SEBS (a polymer combining the rigidity of styrene with the elasticity\nof ethylene–butylene). Subsequently, cross-linking PPBP-pTP\nand SEBS yielded x-(PPBP-pTP)-SEBS membranes with pronounced microphase\nseparation. Additionally, x-(PPBP-15-pTP)-SEBS, with the 15% of PPBP\ncontent, exhibited the high OH<sup>–</sup> conductivity (126.71\nmS/cm at 80 °C); excellent mechanical properties (tensile strength\n= 24.91 MPa and elongation at break = 57.59%); exceptional alkaline\nstability (100% conductivity retention in 2 M KOH at 80 °C after\n960 h); and an excellent AEMWE cell performance of 2.67 A/cm<sup>2</sup> at 1.8 V, using a non-noble catalyst for Ni-based oxygen evolution\nreaction applications.