Gas transport properties of new aromatic poly(ether amide)s containing cyclohexylidene moiety

A series of semifluorinated aromatic poly(ether amide)s (PA) were prepared from a new diamine; 1,1-bis-[4′-{2″-trifluromethyl 4″-(4″′-aminophenyl)phenoxy}phenyl]cyclohexane with five structurally different aromatic diacids. The PAs were characterized by elemental analysis, NMR, FTIR, GPC and thermal techniques. The polymers exhibited very good thermal and mechanical properties (441 °C for 10% weight loss in air, glass transition temperatures ranging from 239 to 258 °C and tensile strengths up to 86 MPa). Gas transport properties of these membranes were investigated for the four different gases (e.g., CH4, N2, O2 and CO2). These membranes showed good gas selectivity with comparable permeability with previously reported aromatic polyamides. PA ‘6A’ showed high CO2 and O2 permeability (30.40 and 6.30 Barrer respectively) and PA ‘6E’ showed high permselectivity for CO2/CH4 (64.29) and O2/N2 (10.67) gas pair. The effect of the presence of the cardo cyclohexylidene unit in the PA membranes towards the thermal, mechanical and gas permeation properties were correlated.

► Poly(ether amide) membranes containing cycloaliphatic moiety. ► High gas selectivity with moderately high gas permeability. ► Structure–property correlation. ► Comparison of gas permeability and selectivity from the Robson plot.