Synthesis of new mono/di-cationic benzimidazolium ionic liquids and their effect on physicochemical properties of PBI membrane

This work aims to synthesize new benzo[d] imidazol-3-ium-based ionic liquids and to examine their effect on the performance of polybenzimidazole (PBI)-based membranes. New mono-cationic and di-cationic ionic liquids with different anions were synthesized through a solvent-free method. The successful synthesis of ionic liquids was validated by FTIR, 1 H-NMR, 13 C-NMR, and TGA. Then, composite membranes were fabricated by employing PBI in conjunction with mono or di-cationic ionic liquid containing different anions such as Br - , HSO 4 - , CF 3 SO 3 - , and BF 4 - utilizing a solution casting technique. Besides, a nanocomposite membrane was prepared with the incorporation of di-cationic ionic liquid immobilized on SiO 2 nanoparticles (DH@ SiO 2 ) in PBI. The findings indicated that all membranes have good oxidation stability in the Fenton test. The thermal stability of the prepared membranes shows no significant change with the incorporation of ionic liquids. Nanocomposite membrane with 2.5 wt% of DH@ SiO 2 exhibited lower degradation in the Fenton test and high conductivity of 78 mS/cm at 80 °C and 105 mS/cm at 120 °C.