Year: 2026
Type: preprint
Abstract: Chemical degradation reshapes the hydrated ion-transport channels of anion exchange membranes (AEMs), but conventional aging measurements do not reveal how their nanostructure evolves toward functional failure. Here we resolve this structural evolution using high-resolution kinetic Monte Carlo (kMC) simulations. The simulations are calibrated to reproduce the experimental ion exchange capacity (IEC) and water uptake (WU) over a month degradation of a PPO-TEA membrane. The ionomer-peak position remains essentially unchanged even after 70% cation loss, while the water channels narrow from approximately 0.8 to 0.6 nm and progressively fragment. The hydrated network loses percolation at a critical hydrophilic volume fraction 𝜙!≈ 0.26, close to the threshold (𝜙!≈ 0.25) inferred from experimental conductivity using a percolation power law. Two complementary descriptions, a percolation law and a connected-carrier model, reproduce the normalized conductivity decay without using conductivity to calibrate the degradation kinetics. These results link conductivity failure to the loss of connected transport pathways within a membrane that retains its characteristic phase-separation length scale. The structural predictions are similar for two kinetic models with different dependencies on local hydration. Thus, a persistent ionomer-peak position can conceal substantial deterioration of the ion-transport network. Resolving channel connectivity along the aging trajectory provides a structural measure of membrane durability that complements conventional characterization of phase separation.
Source: ChemRxiv
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221521450