Data for: "Product Hydrophilicity, Not Reaction Chemistry, Governs Performance Loss in Degraded Anion Exchange Membranes"

Anion exchange membranes degrade through multiple concurrent chemical pathways that are difficult to deconvolve experimentally, leaving their individual contribution to performance loss unresolved. Here we use molecular dynamics and grand-canonical Monte Carlo simulations to isolate SN2 degradation—the most ubiquitous degradation mode—as an independent variable in a model anion exchange membrane, and quantify its impact on water uptake, nanostructure, channel connectivity, ionic conductivity, and water diffusion. We find that SN2 degradation has no independent structural effect beyond the dehydration it causes: degraded and pristine membranes are indistinguishable at equal water content. The water uptake vs ion ex-change capacity agrees quantitatively with experimental Hofmann elimination data—whose product is a tertiary amine rather than the alcohol produced by SN2—establishing that performance loss is set by the hydrophilicity of the degradation product rather than its specific chemistry. We show that conductivity collapses below a critical hydrophilic volume fraction ϕc≈ 0.25, irrespective of degradation mechanism. At extreme degradation, water diffusivity is preserved while ionic conductivity collapses, establishing that conductivity alone is an incomplete indicator of membrane state. This decoupling identifies water transport capacity as an independent design target alongside IEC retention for suppressing the dehydration-driven feed-back that drives membrane failure.