The poly(ethylene oxide) (PEO) was introduced by the cross-linking method in the commercial Matrimid 5218. The two kinds of membranes were prepared from the Matrimid 5218 and the cross-linkers poly(propylene glycol) block poly(ethylene glycol) block poly(propylene glycol) diamine (PPG/PEG/PPGDA) with different molecular weights. The cross-linking reaction process was monitored by FrIR. The cross-linked Matrimid 5218 membranes display excellent CO2 permeability and CO2/light gas selectivity. The effects of cross-linkers with different molecular weights on gel content, thermal properties and H-2, CO2, N-2 and CH4 gas transport properties were reported. The effect of temperature on gas transport properties was also reported, and the permeabilities of these materials as a function of temperature were compared with other gas membrane materials. (C) 2008 Elsevier B.V. All rights reserved.