Hydrophobicity Regulation of Hyperbranched Poly(Aryl Piperidine) Anion Exchange Membranes for Fuel Cells

As a key component of anion exchange membrane fuel cells, anion exchange membranes (AEMs) must exhibit outstanding comprehensive performance. Hyperbranched AEMs have garnered increasing attention due to their superior hydroxide conductivity compared to linear AEMs. However, while the loose chain entanglement of hyperbranched AEMs effectively reduces the mass transfer resistance, it also leads to excessive water uptake and high membrane swelling. Herein, a series of alkyl chains with different lengths are introduced into the hyperbranched AEMs to regulate their hydrophobicity, further affecting the membrane performance. Enhancing hydrophobicity effectively controls water absorption (52.8–15%@80 °C) and achieves extremely low membrane swelling (4.6%@80 °C). Although hydroxide conductivity is impacted by the enhanced hydrophobicity, hbQPTP-Cn AEMs still maintain high ion conductivity (>200 mS/cm@80 °C) due to the construction of ionic clusters induced by the hydrophobic phase. Regulating the hydrophobicity of AEMs also benefits the enhancement of alkaline resistance and water management during fuel cell operation.