A number of imidazole-based acidic (?(LA)>= 0.6) ionic liquids (RmimCl-LA, where R = Et or Bu, LA = AlCl3, AlBr3, (BuAlCl2)-Bu-i, FeCl3, GaCl3, and BBr3) has been synthesized and their activity in cationic polymerization of isobutylene has been assessed. Among different ionic liquids tested here, emimCl-AlCl3, emimCl-FeCl3 and emimCl-GaCl3 showed the best results in terms of monomer conversion, exo-olefin end group content and polydispersity. It was shown that reaction rate depended strongly on the rate of partial hydrolysis of corresponding ionic liquid and increased in the following order: emimCl-FeCl3 < emimCl-GaCl3 < emimCl-AlCl3. It was demonstrated that emimCl-FeCl3 is the most promising catalyst for the synthesis of HR PIB with desired low molecular weight (M-n < 2500g mol(-1)) and polydispersity (M-w/ M-n < 2.5) and high content of exo-olefin end groups (> 85%). However, due to poor dispergation of emimCI-FeCl3 in n-hexane as well as its high stability toward hydrolysis, the catalyst aging and/or sonication of reaction mixture is required in order to provide acceptable polymerization rate. (C) 2018 Elsevier Ltd. All rights reserved.