Gas transport properties of new aromatic polyimides based on 3,8-diphenylpyrene-1,2,6,7-tetracarboxylic dianhydride

Three novel polyimides have been successfully synthesized from 3,8-diphenylpyrene-1,2,6,7-tetracarboxylic dianhydride (DPPD), and three commercial diamines by solution polycondensation. All polymers exhibited high molecular weight, high thermal stability and high rigidity (no glass transition was detected up to 400°C) and free volume. The new polymers have been tested as gas separation membranes, showing very good combination of permeability and selectivity, especially in the case of the polymer derived from trimethyl-m-phenylenediamine (TMPD), which overpassed the 1991 Robeson upper bound for the gas pairs O2/N2 and CO2/CH4 and was near the 2008 upper bound for CO2/N2. [Display omitted] •A planar and rigid dianhydride has been used to prepare gas separation polyimides.•PCO2/PHe and PCH4/PN2 ratios are reversed compared to glassy polymers (as in PIMs).•Very high permeability has been attained by combining with ortho-substituted diamines.•Meta-substitution in diamine significantly improves permeability.•New polyimides show excellent combination of permeability and selectivity for CO2/N2.