AbstractThe gas (oxygen and nitrogen) transport characteristics of the IPN membranes of polyurethane/polysturene were studied. The effect of synthesis temperature, composition, and crosslink density of the IPN membranes were analyzed. Polyurethane was prepared thermally and polystyrene was prepared by photolytic polymerization methods at various temperatures. The degree of intermixing between component polymers in the IPN membrane increased with decreasing synthesis temperature from 50°C to −10°C. The PS phase Tg was shifted inwardly up to 12°C. The permeability coefficient decreased and ideal separation factor increased also with decreasing the synthesis temperature due to the increase of miscibility. The permeability coefficient of oxygen and nitrogen ranged in the 10−10and 10−10order of magnitude. The permeability coefficient showed the minimum value and the ideal separation factor showed the maximum value at about 40 wt% polyrethane composition. The permeability data agreed well with the simple free volume model proposed by