Copolymers composed of D-glucopyranosyl-alpha(1'- 6)-2-deoxy-2-methacrylamido-D-mannitol (MAGPM) and D-glucopyranosyl-alpha(1'--> 6)-2-deoxy-2-methacrylamido-D-sorbitol (MAGPS) as a vinyl saccharide monomer and methyl methacrylate were synthesized. The permeability of dissolved oxygen through the copolymer membranes was determined. Based on the two-state model, the content and spin-lattice relaxation time of the hydration water were determined using DSC and O-17 NMR. The water uptake of the copolymer membranes was improved significantly by the vinyl saccharide units. The sample with the highest water content (72.1 wt.%) in our study maintained a good transparency in the wet state and the permeability of dissolved oxygen through it was 5.96x10(-10) cm(3)(STP) cm/s cm(2) cm Hg at 35 degrees C. With an increasing volume fraction of water, an inflection point was observed in the water uptake and in the permeability of dissolved oxygen through the concerned copolymer membrane, and the spin-lattice relaxation time of water in the copolymer membranes and the mobility of the hydration water increased. Free water in the copolymer membranes gradually increased above the inflection point. It is concluded that the increase in the permeability of dissolved oxygen through the copolymer membranes was caused by two factors: (1) plasticization of the copolymers by the hydration water, and (2) oxygen permeation in free water taken up by the copolymer membranes and then the aggregation of water enclosed by a large amount of the hydrophobic MMA units dispersed in all copolymer membranes.