In this paper, the solubility of several modified poly(propylene oxide) (PPO) derivatives and silicones has been investigated by measuring cloud point pressure (CPP) values in supercritical carbon dioxide (Sc CO2) at a temperature range of 308-328 K and in the pressure range of 7.40-23.00 MPa. The end group and molecular weight strongly affect the solubility of the PPO derivatives. The solubility of modified silicones in Sc CO2 is generally larger than that of polyethers of the same chain length. In addition, the solubility of some silicones with pendant phosphine groups in Sc CO2 was also determined. The CPP values of the phosphine-modified silicone oils increases with the number of phosphine side chains along the silicone backbone. The relationship between the solubility and structure of the PPOs and silicones is discussed. (c) 2007 Elsevier B.V. All rights reserved.