Hydrophobicity\nRegulation of Hyperbranched Poly(Aryl\nPiperidine) Anion Exchange Membranes for Fuel Cells

As a key component of anion exchange membrane fuel cells,\nanion\nexchange membranes (AEMs) must exhibit outstanding comprehensive performance.\nHyperbranched AEMs have garnered increasing attention due to their\nsuperior hydroxide conductivity compared to linear AEMs. However,\nwhile the loose chain entanglement of hyperbranched AEMs effectively\nreduces the mass transfer resistance, it also leads to excessive water\nuptake and high membrane swelling. Herein, a series of alkyl chains\nwith different lengths are introduced into the hyperbranched AEMs\nto regulate their hydrophobicity, further affecting the membrane performance.\nEnhancing hydrophobicity effectively controls water absorption (52.8–15%@80\n°C) and achieves extremely low membrane swelling (4.6%@80 °C).\nAlthough hydroxide conductivity is impacted by the enhanced hydrophobicity,\nhbQPTP-Cn AEMs still maintain high ion conductivity (>200 mS/cm@80\n°C) due to the construction of ionic clusters induced by the\nhydrophobic phase. Regulating the hydrophobicity of AEMs also benefits\nthe enhancement of alkaline resistance and water management during\nfuel cell operation.