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

Abstract

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 paraterphenyl (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/cm 2 at 1.8 V, using a non-noble catalyst for Ni-based oxygen evolution reaction applications.