A novel silicone polymer membrane with facilitated oxygen transport properties was prepared by using 11-alkene acid cobalt, a silicone rubber containing vinyl groups of 5 mol %, a hydrogen-containing silicon oil, and chlorine platinum acid. The solution casting and the vulcanization were carried out simultaneously at room temperature. Investigation showed that PO2 increased and PN2 did not change with decreasing gas pressure difference. This facilitated oxygen transport behavior was contributed by a polymeric cobalt complex formed from carboxylic groups and cobaltous ions in the membrane to result in the simultaneous increase of both P-O2 and alphaO(2)/N-2 under lower gas pressure difference. For example, the PO2 and alphaO(2)/N-2 of the membrane containing 11-alkene acid cobalt of 2.5 wt% were 750 Barrer and 3.09 under a gas pressure difference of 0.05 mPa. As much as 5 wt% 11-alkene acid cobalt could be added to the membranes; PO2 and alphaO(2)/N-2 increased to 802 Barrer and 3.34 respectively when the membrane contained 11-alkene acid cobalt of 5 wt %. (C) Wiley Periodicals, Inc.