A series of fully aromatic polyamides (PAs) was prepared by the polycondensation reaction of 4,4'-diamino-4-tritylaniline with four commercial diacids. The polymers were well-characterized using different analytical tools and membranes were prepared from the PM using a solution cast method. The resulting PM exhibited good mechanical properties, with a tensile strength up to 74 MPa, thermal stability, and a high glass transition temperature. The gas permeation properties of different gases through the PA membranes were investigated using a constant-volume method. The incorporation of a trityl group into the polymer backbone offers a successful approach to improve the gas permeabilitiy with P-co2 and P-o2 values as high as 141.0 and 33.4 Barrer, respectively. The PA membranes also exhibited a reasonably high permselectivity for the separation of important gas pairs CO2/CH4 and O-2/N-2. The efect of a trityl-substituted triphenylamine (TPA) and its spatial arrangement and size-distribution function of the free volume on gas transport properties were calculated using molecular dynamics (MD) simulation. Gas difusivity is supported by individual penetrant molecule trajectories and mean-square displacements in a polymer matrix. MD simulations were consistent with the experimental data. (C) 2016 Elsevier B.V. All rights reserved.