Gas transport property of the binaphthyl-based polyimide membranes

There is constant need for improving the performance of gas separation membranes for making the membrane technologies viable for industrial applications. In this work, we introduce an array of novel polyimide (PI) membranes containing binaphthyl moieties for gas separations. Using two different methods, chemical or azeotropic imidization, we have synthesized PIs with hydroxyl (OH) group or acetate (OAc) groups based on binaphthyl diamine and three different di-phthalic anhydride monomers (6FDA, BTDA, and ODPA). Perme-abilities of H-2, CO2, O-2, N-2 and CH4 were evaluated on six membranes under 0.2 MPa. The contorted binaphthyl PIs are able to sieve small gas molecules in general. Bulky OAc side groups in PI increase free volume via preventing the polymer chains from packing and cause higher gas permeability. The new binaphthyl-based polyimide architecture is developed for a possible application in gas separation.