Polymeric ionic liquids based on ether functionalized ammoniums and perfluorinated sulfonimides

A new family of polymeric ionic liquids (PILs) based on alkyl and alkyl ether substituted ammoniums and perfluorinated sulfonimides (i.e., bis(fluorosulfonyl)imide (FSI⁻), and bis(trifluoromethanesulfonyl)imide (TFSI⁻)) have been synthesized by polymerization of the corresponding ionic liquid monomers (ILMs). Their structures and compositions have been characterized by ¹H and ¹⁹F NMR, FTIR and viscosity-average molecular weight (M_v). The physicochemical properties of both the ILMs and the PILs have been studied in terms of thermal stability, phase transition, and ionic conductivity. All the prepared ILMs and PILs reveal excellent thermal stabilities to greater than 250 °C. The PILs containing alkyl ether side unit show significant decrease in glass transition temperature (T_g), the values of T_g of the alkyl ether based-PILs are all significantly lower by 10–77 °C in magnitude than those of the corresponding alkyl based ones. The ionic conductivity of alkyl ether based-PILs in the best case increases up to 4.0 × 10⁻⁶ S cm⁻¹ at 30 °C, and reaches 7.6 × 10⁻⁵ S cm⁻¹ at 60 °C, and outperform their ammonium counterparts with alkyl side chain that were synthesized as references.