Ionic liquid modified poly(2,6-dimethyl-1,4-phenylene oxide) for CO₂ separation

Ionic liquid modified poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was synthesized by introducing imidazolium-based, pyridinium-based, and ammonium-basd ionic liquid groups to the methyl position of PPO. Membranes were prepared from the different types of ionic liquid modified PPO (IPPO), and the permeability of CO₂ and N₂ in these membranes was characterized. For having the CO₂-philic ionic liquid groups in the structure, the CO₂ solubility of the IPPO is better than that of PPO, while the CO₂ diffusivity in the IPPO is proportional to glass transition temperatures. The adsorption and desorption of CO₂ in the IPPO were also investigated, and the results manifest that the adsorption and desorption of CO₂ in IPPO are completely reversible, which makes the polymer promising as solid adsorbent materials for CO₂ separation.