The impregnation of ibuprofen into submicron films (25-250 nm) of poly(methyl methacrylate), PMMA, under supercritical CO2 conditions (at 40 degrees C and 50 degrees C and 13.8 and 20.7 MPa) was studied. The quartz crystal microbalance (QCM) was used to perform real-time, in situ impregnation measurements. The amount of ibuprofen uptake into the polymer film was calculated directly from the QCM results. Different aspects of the process were studied including: the effect of CO2 density on uptake, distribution uniformity across the film thickness, and impregnation rate. The partitioning coefficient of ibuprofen PMMA and CO2 was high, whereas the diffusivity of ibuprofen was found to be order of magnitudes lower than that of CO2. These two effects are believed to result in high drug loading in the polymer. It was also concluded that CO2 helped in producing uniform concentration profiles of ibuprofen in the PMMA films. Finally, preliminary studies on the impregnation of poly(vinyl pyrrolidone), PVP, with ibuprofen were performed. The QCM response in the case of PVP films was significantly larger than that with PMMA at the same conditions. Some possible causes for this unusual behavior are discussed. (C) 2012 Elsevier B.V. All rights reserved.