Preparation and High Performance of Cellulose Acetate Films by Grafting with Imidazole Ionic Liquid

Cellulose acetate (CA) grafted with imidazole ionic liquids (CA-ILs) was synthesized by reacting CA with imidazole ionic liquids ([HO₂CMmim]Cl, [HO₂CEtmim]Cl, and [HO₂CMmim]Br) by using tetrahydrofuran (THF) as the solvent and pyridine as the catalyst. The CA and CA-IL films were fabricated by using the casting solution method. The CA-IL films exhibited good film forming ability and mechanical properties. The successful grafting of CA with imidazole ionic liquids was confirmed by Fourier transform infrared (FTIR), ¹H NMR, scanning electron microscopy (SEM), and elemental analysis, and the grafting degrees were 2.24, 2.45, and 3.30%, respectively. The CO₂ permeation properties of the CA-IL films were 65.5, 105.6, and 88.3 Barrer, increased up to 2.0, 3.2, and 2.7 times, respectively, as compared to pure CA (32.6 Barrer). The CO₂/CH₄ selectivities of the CA-IL films were 15.6, 12.6, and 19.2, increased up to 1.7, 1.4, and 2.1 times, respectively, as compared to pure CA (9.26). Therefore, it can be concluded that the imidazole ionic liquids are immensely useful for improving the gas separation performance of CA films.