A series of copolymers containing ether oxygen groups and amino groups were prepared based on N,N-dimethylaminoethyl methacrylate (DMEMA) and polyethylene glycol methyl ether methyl acrylate (PEGMEMA). The effect of PEGMEMA content in the copolymer on density, free volume, mechanical performance, and H-2, CO2, N-2 and CH4 gas transport properties of the copolymer was determined. Free volume was characterized using the polymer density and group contribution theory. The permeability of the copolymer to CO2 is high, and both the CO2/N-2 and CO2/H-2 selectivities are high. For example, the permeability coefficient of PDMAEMA-PEGMEMA-90 ("90" represents the weight percent of PEGMEMA) to CO2 is 112 Barrer and the CO2/N-2 and CO2/H-2 selectivity coefficients are 31 and 7, respectively. The effect of the temperature on gas transport properties was also determined. Finally, the potential application of the copolymer membranes for CO2/light gases separation was explored. (C) 2007 Elsevier B.V. All rights reserved.