Polyether based thin film composite (TFC) membranes were developed by interfacial polymerization (IP) on polysuylfone (PSf) ultra-filtration membrane with poly (dimethylsiloxane) (PDMS) inter-layer. Polyetheramine (PEA) and Trimesoyl Chloride (TMC) were selected as aqueous monomer and organic monomer, respectively. The thickness of the PDMS inter-layer was 550 nm, while IP separation layer was only 100 nm. The effects of the PDMS inter-layer and the PEA molecular weight on the TFC membrane performance were investigated. The gas permeation results show that the TFC membrane with PDMS inter-layer exhibits higher CO2/N-2 selectivity compared to the membranes without PDMS inter-layer. PDMS inter-layer is able to eliminate the defects on the support membrane and diminish the TMC hydrolysis as well. Among the membranes prepared with three different molecular weight PEAs (ED-600, ED-900 and ED-2003), the membrane of ED-900 exhibits the best performance with an impressive CO2 permeance of 360 GPU and CO2/N-2 selectivity of 67.2 for a mixture CO2/N-2 (20/80 by volume), while for a mixture of CO2/CH4 (10/90 by volume) it demonstrates CO2 permeance of 275 GPO and CO2/CH4 selectivity of 31.6. (C) 2014 Elsevier B.V. All rights reserved.