Poly (aryl piperidinium) membranes with dipolar alkyl nitrile sidechains for fuel cells

Several poly (biphenyl piperidine-trifluoroacetophenone) based polymers with different grafting ratios of polar alkyl nitrile side chains are synthesized, named PBPAp-PN-x. The relationship between structure and performance is studied, including conductivity, swelling ratio (SR), morphology, single-cell performance, etc. The SR and conductivity at 80 °C of PBPAp-PN30% are 41.0% and 142.3 mS cm −1 , whereas those of PBPAp-PN0% are 77.8% and 155.3 mS cm −1 , respectively. Further, molecular dynamics (MD) simulations are carried out to microcosmically reveal the mechanism of structure-property relationship, which simulate the number of water molecules ( N H2O ) and the diffusion coefficients ( D ). The simulations also indicate polar cyanide groups can form close contacts, which is similar to physical crosslinking to inhibit the swelling of backbone. As a result, the advantage of grafting dipolar molecules in AEMs not only effectively resolves the “trade-off” problem between ionic conductivity and dimensional stability, but also might be a promising application in fuel cells.