Molecular Dynamics Study on the Effect of Cyclic Conducting Moieties on Poly(2,6-dimethyl-1,4-phenylene oxide) Anion Exchange Membranes

We investigate PPO quaternized with different azoles (five-membered heterocyclic compounds) with a different odd number of Nitrogen atoms (1N-pyrrole, 3N-1,2,3-triazole, and 5N-pentazole) to form pyrrolium-PPO­(py-PPO), 1,2,3,-triazolium-PPO­(tri-PPO) and pentazolium-PPO­(pen-PPO) AEMs, using molecular dynamics (MD) simulations to compare and evaluate their OH– transport via the vehicular mechanism. OH– diffusivity at the hydration level λ = 12 is 3.10 × 10–10 m2/s, 1.92 × 10–10 m2/s m2/s, and 1.91 × 10–10 m2/s for py-PPO, tri-PPO, and pen-PPO, respectively. This trend is due to the shorter distance between adjacent groups of py-PPO (7.5 Å) leading to an efficient hydroxide transport than tri-PPO (7.8 Å) and pen-PPO (8.1 Å) at λ = 12. Also, this trend is justified by the smaller average number of clusters for py-PPO (1.2), smaller than tri-PPO(2.0), and pen-PPO (1.5) at λ = 12, which suggests better connectivity and hence better conductivity