One of the most promising strategies to improve membrane CO2 permeation rate and CO2/N-2 selectivity with commodity polymeric material is through blending two or more selected polymer materials in the membrane fabrication process. However, the majority of the published studies have focused on blend dense film membranes. In this study, the effects of CO2-philic additives were investigated for blend asymmetric membranes fabricated by the phase inversion technique. We present the preparation and gas transport properties of a series of blend membranes made from commercially available poly (2,6-dimethyl-1,4-phenylene oxide) (PPE) and additives including polyethylene glycol (PEG) and a PEG-PDMS copolymer (commercial name IM22). Compared with the pure PPE membranes, the CO2 permeances of the membranes containing 40 wt% PEG and 50 wt% IM22 were 4 and 5 times higher, respectively. Significant improvement in selectivity was also observed for the blend membranes at lower concentrations of additives. Evaluation of SEM images of membrane cross-sections indicated that the additives significantly increased the porosity of the membrane and decreased the membrane skin layer thickness. XPS analysis of the membrane surface composition indicated a linear relationship between the amount of IM22 on the membrane surface and the total additive loading in the dope solution, while EDX analysis of the Si concentration in the membrane suggested a uniform distribution of IM22 in the bulk membrane structure. (C) 2013 Elsevier B.V. All rights reserved.