Highly Cationized and Porous Hyper-cross-linked Polymer Nanospheres for Composite Anion Exchange Membranes

Hyper-cross-linked polymer (HCP), a category of porous organic materials (POMs), is exploited as an anion conducting membrane via a highly cationized and porous quaternized ammonium triptycene-based HCP in the form of <100 nm nanospheres (QTP-HCP-NS) for the first time. The material possesses a high ion density of 3.65 mmol g(-1) as well as a high Brunauer-Emmett-Teller (BET) surface area of 706 m(2) g(-1). Anion exchange membranes (AEMs) are prepared by mixing different loadings of QTP-HCP-NS with quaternized poly(phenylene oxide) (QPPO) and compared with a compressed QTP-HCP pellet. Owing to the high ion density and high water sorption, which results in abundant ion conduction channels in QTP-HCP, the ion conductivity of the composite AEMs is enhanced by 79.5% compared with the unfilled QPPO membrane and by 677% compared with a compressed QTP-HCP pellet. In addition, lower dimensional swelling and higher tensile strength are achieved for the composite AEMs. Aggregation and the resulting interfacial defects of QTP-HCP-NS are found in the composite AEM at a high loading and in the comparative compressed pellet, causing a significant reduction in ion conduction and mechanical properties.

Automated summary

The study introduces a novel anion conducting membrane using QTP-HCP-NS for the first time, demonstrating improved ion conductivity and mechanical properties compared to traditional membranes. The composite AEMs exhibit lower dimensional swelling, higher tensile strength, and significantly enhanced ion conductivity, thanks to the unique properties of QTP-HCP-NS. However, aggregation and interfacial defects at high loadings of QTP-HCP-NS may lead to a reduction in ion conduction and mechanical strength.