Chain-scission degradation mechanisms during sulfonation of aromatic polymers for PEMFC applications

Highlights: • Sulfonation chain-scission mechanisms of aromatic polymers are studied using DFT calculations. • Transition states are optimized and activation energies are evaluated. • Solvation effect are evaluated based on implicit solvation model. The direct sulfonation is a cheap process but introduces the valuable sulfonic acid groups onto the backbone of aromatic polymers for proton exchange membrane fuel cell applications. However, the chain-scission during sulfonation degrades the polymer backbone by cleavage of the linkages between the arylene rings. If the sulfonation is conducted at a relatively high temperature for long time, the degradation may be significant. In this paper, the chain-scission mechanisms of the typical aromatic polymers are studied in terms of transition states and activation energies using density functional theory calculations, and the improvement of the overall performances of sulfonated proton conducting materials is discussed.