Block copolyimides based on aromatic dianhydrides and diamines copolymerized with diamino room temperature ionic liquid (RTIL) monomers were synthesized over a range of compositions Specifically, two diamino RTILs, 1,3-di(3-amino-propyl) imidazolium bis[(trifluoromethyl)sulfonyl] imide ([DAPIM] [NTf2]) and 1,12-di[3-(3-aminopropyl) imidazolium] dodecane bis[(trifluoromethyl) sulfonyl] imide ([C-12 (DAPIM)(2)] [NTf2](2)) were synthesized using a Boc protection method The two RTILs were reacted with 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) to produce 6FDA-RTILs oligomers that formed the RTIL component for the block copolyimides The oligomers were reacted with 6FDA and m-phenylenediamine (MDA) at oligomer concentration from 6 5 to 258 mol % to form block copolyimides Increasing the concentration of the 6FDA-RTIL oligomer in the block copolyimides resulted in a decrease in the thermal degradation temperature, glass transition temperature and an increase in the density The gas permeability of the RTIL based block copolyimide decreased but the ideal permeability selectivity for CO2/CH4 gas pair increased relative to the pure 6FDA-MDA (C) 2010 Wiley Periodicals, Inc J Polym Sci Part A Polym Chem 48 4036-4046, 2010