The micellization of PEO-PPO-PEO block copolymers in p-xylene has been studied in the presence Of CO2. With the application Of CO2, some copolymers with suitable molecular weights and EO ratios can form reverse micelles with critical micellization pressure up to 5.8 MPa. For the copolymers with the same length of PO block, higher EO ratios facilitate reverse micelle formation. For the copolymers with the same composition, higher molecular weight is favorable to form reverse micelles. With the suitable composition and molecular weight, the critical micelle pressure (CMP) of copolymers decreases with the increase in the lengths of PEO and PPO blocks due to the hydrophilic and folding effects, respectively. Both the EO ratios and the molecular weights are important for the formation of reverse micelle. The reverse micelle solution can solubilize water with W-0 (molar ratio of water to EO segment) up to 3.3. (C) 2004 Elsevier Inc. All rights reserved.