Supercritical fluid (SCF) technology has emerged as a novel method of substance extraction in industry. Temperature and pressure induced density fluctuations give SCFs properties that are between those of a gas and a liquid, thus making them ideal solvents. Here we focus on the effects of supercritical carbon dioxide (scCO2) on surface segregation in polymer blends. Present techniques for polymer separation require exposure to high temperatures for long periods of time, which causes sample degradation. SCFs have the ability to extract substances at lower temperatures and with greater speed. We wanted to determine the effects of supercritical fluids on polystyrene and deuterated polystyrene (PS/dPS) blends after exposure to four different pressures (800, 1200, 1450, and 2000 psi) at two different temperatures (36°C, 50°C). Under these conditions, we expected the polymers to phase segregate without any degradation of the polymer blend. The two polymers were dissolved in toluene and diluted to four different concentrations. Samples were exposed to scCO2 and segregation was examined via Secondary Ion Mass Spectrometry (SIMS). In addition, the degree of dPS mobility was determined through bilayer PS/dPS samples. SIMS data revealed that segregation of dPS from PS occurred at the silicon substrate rather than at the surface. The control deuterium profile was flat (Figure 1), whereas after 24 hours a peak was distinctly visible (Figure 2), indicating that segregation had occurred. Bilayer deuterium profiles also indicated dPS mobility. The data suggests that dPS migration occurs more readily at 50ºC than 36ºC, and most effectively along a 1450 psi isobar. Future work will involve an investigation as to how scCO2 affects segregation in polyethylene (PE)/dPS blends, as well as in PE/trans fatty acid blends. Future project applications involve a novel method to extract trans fatty acids from specific foods using SCFs in the hope that one day these foods can be consumed without the fear of contamination by hazardous fatty substances. This research was supported by grants from the Simons Foundation and Garcia MRSEC.