Beneficial use of hyperbranched polymer in cross‐linked anion exchange membranes for fuel cells

A series of cross-linked blend membranes based on a linear poly(2,6-dimethyl phenylene oxide) (PPO) and a hyperbranched poly(4-vinylbenzyl chloride) (HVBC) are prepared via a simple solution casting procedure, followed by a cross-linking treatment. The experiment indicates that the “HVBC enhancing PPO” membranes can have a looser cross-linked “linear-hyperbranched” blend structure, which is expected to improve the water absorption and dimensional stability. As a result, the excellent overall properties including high anion conductivity, low swelling, high strength, and excellent oxidative-alkaline stability can be achieved simultaneously. A maximum conductivity of PPO-HVBC-100 (ion exchange capacity [IEC] ~ 1.88 mmol/g) is up to 135.9 mS/cm at 80°C, which is 2.9 times higher than that of pristine PPO membrane (IEC ~ 1.62 mmol/g). All the results reveal that the hyperbranched HVBC with a unique multi-cation structure is a preferred “performance-enhancing component” for the PPO-based membranes, and this study also provides a novel idea for the preparation of high-performance AEMs.