The chemical stability of phosphonium-based ionic liquids under gamma irradiation

The effects of gamma-radiation on the physicochemical and ion transport properties of phosphonium-based ionic liquids (ILs) were investigated. Five ILs that have different physical properties of hydrophobicity, viscosity and conductivity were studied. Gaseous radiolysis products were analyzed using GC-MS, and the IL phase was analyzed using UV-vis, NMR, FTIR and Raman spectroscopy, and conductivity measurement. The results show that the ILs are relatively resistant to radiolytic degradation, but measurable quantities of small organic species are formed. These arise from the radiolytic dissociation of the P-C bond in the cation moiety. These small organic molecules induce agglomeration within the IL and this results in substantial changes to some of the IL properties.