Temperature-dependent structure changes in Nafion ionomer studied by PCMW2D IR correlation spectroscopy

Temperature-dependent infrared (IR) spectra of a Nafion membrane were measured over a temperature range from 30 to 320 °C. The obtained spectra were analyzed using perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy and quantum chemical calculations (QCC). Three-step structural changes in Nafion ionomer induced by temperature were revealed. Dehydration of the ionomer is dominant below 60 °C. Protonation of sulfonate group in the side chain terminal occurs around 100 °C. Thermal degradation of the chains starts above 280 °C.