Infrared and thermal behaviour of proton exchange membrane (PEM) after cationic contamination

This paper focuses on the differences between the thermal behaviour of cation exchanged membrane based on Short Side Chain (SSC) and Long Side Chain (LSC) polymers. The α relaxation of alkali and Cu2+ exchanged membranes showed dependency on ion exchange capacity and the length of the side chain similar to that of H+-form membranes. The modulus drop of multivalent contaminated membranes was attributed to a degradation process except for Ba2+and Zn2+ LSC exchanged membrane. The thermal behaviour as function of the Lewis Acid Strength, LAS, of the cation could originate from infrared (IR) vibrational changes. For cations with LAS<0.3, the 1060 cm−1 and 970 cm−1 mode induce concurrent shift towards high wavenumbers. This suggests a stiffening of the corresponding bonds resulting in the improvement of the membrane's thermal stability. The cations with LAS>0.3 decrease the 970 cm−1 wavenumber which could explain the enhancement of the degradation.

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► Interaction between PFSA and cation are controlled by Lewis Acid Strength (LAS).
► A critical value for LAS of cation is 0.3.
► Cations impact on thermal properties of LSC and SCC PFSA.
► IEC Effect on monovalent cation and Cu2+-exchanged membrane