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. [Display omitted] • PBP-based AEMs tethered with dipolar molecular side chains were synthesized. • Investigating the effect of intermolecular interaction on the performance of AEMs. • Solving the "trade-off" problem between dimensional stability and ionic conductivity. • Molecular dynamics provides the effect of polar molecules on AEMs performance. [ABSTRACT FROM AUTHOR]