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

Thabakgolo T Letsau; Takuya Mabuchi; Phumlani F Msomi

doi:10.1021/acsomega.3c05291

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

ACS Omega. 2023 Dec 12;8(51):48711-48718. doi: 10.1021/acsomega.3c05291. eCollection 2023 Dec 26.

Authors

Thabakgolo T Letsau^{1

2}, Takuya Mabuchi^{3

4}, Phumlani F Msomi^{1

2}

Affiliations

¹ Department of Chemical Science, University of Johannesburg, PO Box 17011, Doornfontein, 2028Johannesburg ,South Africa.
² Research Centre for Synthesis and Catalysis, Department of Chemical Science, University of Johannesburg, PO Box 17011, Doornfontein, 2028Johannesburg ,South Africa.
³ Frontier Research Institute of Interdisciplinary Sciences, Tohoku University, Sendai ,Miyagi9808577, Japan.
⁴ Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.

Abstract

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.