Defect-free high performance membranes for O-2/N-2 separation were prepared by coating the porous polyethersulphone (PES) membrane of hyperthin-skin layer with silicone rubber. The combined effects of fabrication parameters in dry/wet phase inversion process and of the casting dope rheology enabled improved of membrane performance in O-2 and N-2 separation, i.e. the optimum range was found to be from 149 to 447 s(-1) and 10 to 14 s, respectively, for the shear rate and the evaporation time to prepare the hyperthin-skinned asymmetric polyethersulfone membranes. The optimum polymer concentration was 32 wt.%, 61 wt.% and 7 wt.% for PES, 1-methyl-2-pyrrolidone and water respectively. The thinnest skin layer thickness was 538 +/- 95.6 angstrom. Evaporation time and casting shear have been identified as the dominant fabrication parameters in controlling skin layer thickness and skin integrity. (C) 2010 Elsevier B.V. All rights reserved.