Polymer membranes were prepared by radical polymerization of the 1,4,7,10-(tetraoxacyclododecan-2-yl) methyl methacrylate (CR4MA) monomer and a small quantity of a cross-linking agent ethyleneglycoldimethacrylate. High vacuum pressure techniques were used to evaluate oxygen and helium transport through these membranes at temperatures below and above its glass transition temperature, between 0 and 50 degreesC. The apparent values of both the permeability and diffusion coefficients are unusually low because of the high packing degree of these polymeric membrane materials. The results obtained were also compared with those deter-mined for polymer membranes derived from their open chain counterparts, the polymer derivatives from methacrylate monomers with a number of oxyethylene units in the ester residue variable between 2 and 6, and with a set of other polymers. (C) 2003 Published by Elsevier Ltd.