Spiro[fluorene-9,9′-xanthene] containing fluorinated poly(ether amide)s: Synthesis, characterization and gas transport properties

[Display omitted] •Spiro[fluorene-9,9′-xanthene] based poly(ether amide)s (PAs) were synthesized.•PAs displayed low dielectric constant and high optical transparency.•PAs showed good thermal stability and good mechanical properties.•PAs showed high permselectivity (PO2/PN2∼8.85 and PCO2/PCH4∼35.43). A new diamine monomer, 2′,7′-bis-[2″-trifluoromethyl 4″-(4‴-aminophenyl)phenoxy]-spiro[fluorene-9,9′-xanthene] was successfully used to synthesize several polyamides (PAs) for membrane-based gas separation applications. All synthesized polymers were soluble in organic solvents, exhibited high molecular weight, high thermal stability (up to 483°C and 519°C in air and nitrogen respectively, for 10% weight loss) and high glass transition temperature (273–289°C). The optically transparent membranes (λcut-off⩾364nm) from these PAs showed tensile strength up to 88MPa with elongation at break up to 12%. In general, the membranes prepared from these polymers showed very good combination of permeability and permselectivity for a pair of gases. It has been attempted to draw a structure–property correlationship between the chemical structures of the polymers and their gas transport properties on the basis of their FFV, glass transition temperatures, intersegmental distance and dielectric constant values.