Kinetic Monte Carlo Framework for Coupled Degradation and Dehydration of Anion Exchange Membranes

Kinetic Monte Carlo (kMC) simulations, augmented with temporal-acceleration schemes, can efficiently handle stiff reac- tion–transport networks when fast processes rapidly relax to quasi-equi- librium on a fixed lattice. However, in glassy anion-exchange mem- branes (AEM), rare and irreversible chemical degradation events con- tinuously reshape the nanoscale morphology, and the associated hydra- tion and transport degrees of freedom remain far from a well-defined lo- cal equilibrium. This combination of evolving state space and non-equil- ibrated fast dynamics lies outside the scope of existing kMC acceleration frameworks. To address this challenge, we introduce an auxiliary-parti- cle kinetic Monte Carlo (AP-kMC) scheme. In AP-kMC, short-lived mobile particles spawned at degradation sites execute hop, water-elimi- nation, and decay moves, enforcing rapid local relaxation of the hydra- tion structure while preserving the stochastic rules of kMC. Parameter- ized with molecular-dynamics morphologies and experimental solution degradation kinetics, AP-kMC reproduces the evolution of ion-ex- change capacity, water uptake, and conductivity, and reveals a feedback loop in which poorly hydrated sites degrade first and each degradation event induces further local dehydration. The resulting thinning and frag- mentation of water channels cause loss of hydrophilic percolation and abrupt conductivity collapse well before complete charge loss. AP-kMC thus reframes AEM durability as a coupled degradation–drying–perco- lation problem and provides a transferable strategy to simulate reactive, out-of-equilibrium polymer electrolytes where local solvation controls reactivity.