Bent-twisted block copolymer anion exchange membrane with improved conductivity

Inadequate hydroxide conductivity of anion exchange membrane (AEM) is one of the obstacles restricting practical application of anion exchange membrane fuel cell. In this work, we report the design, fabrication and properties of AEMs based on bent-twisted non-coplanar block copolymer. The bent-twisted polymer backbone creates high free volume size so that hydroxide ion transport is facilitated. The free-volume effect can also facilitate microphase separation due to enhanced chain segment motion. With the free-volume holes working synergistically with microphase-separation enabled ion channels, the membrane showed a high conductivity (35 mS cm−1 at room temperature) at a relatively low ion exchange capacity (IEC, 1.25 meq g−1); it also exhibited a good dimension stability, the swelling ratio being 4.7% at room temperature and kept virtually unchanged with temperature because of relatively low IEC. A H2/O2 fuel cell employing the fabricated AEM yielded a high power density (262 mW cm−2 at 50 °C). Our work opens up a new route to fabrication of highly conductive AEM with relatively low IEC.