Alkyl-Imidazolium Functionalized Poly(ether ketone)s: Synthesis and Their Application for Gas Separation

Imidazolium-based ionic liquids have attracted significant attention for the CO2/light gas separation due to their electrical intera-ction with the quadrapole moment of CO2. Here we present alkyl imidazolium-functionalized poly(ether ketone)s (Im-PEKs) as novel polymer membranes for CO2/N2 and O2/N2 separations. The Im-PEK polymers were synthesized by polycondensation between difluoro- and dihydroxy-monomers, followed by benzylic bromination and alkyl imidazolium-functionalization. The polymers with  pendant imidazolium-based ionic salts showed high CO2 solubility and hence a very high CO2/N2 permselectivity due to their  high solubility selectivity. In addition, the Im-PEK with long alkyl chain ([C12-Im-PEK][Br]) displayed an extraordinary high O2/N2 permselectivity of 15.5 due to its enhanced diffusivity selectivity. The Im-PEK membranes also displayed good thermal and mechanical stabilities as well. The synthesis of the IL-PEKs and their properties will be discussed in detail.