Solubility and diffusivity of cosolvents and carbon dioxide in a photoresist polymer have been measured below the glass transition temperature by the inverse gas chromatography and static capsule methods over a temperature range of 75-100 degrees C and pressures up to 7000 kPa. The results showed that presence of even low pressures of CO2 increased the solubility and diffusivity of the cosolvents studied. Experiments in which exposure of the polymer to CO2 was cycled on and off indicated that the free volume introduced by the CO2 persisted in the polymer for a significant time after removal of the CO2. (c) 2008 Wiley Periodicals, Inc.