Using NMR spectroscopy and NMR imaging, the behaviour of polymers in supercritical CO2 (sc-CO2) using a custom-made cell designed from poly(ether ether ketone) (PEEK) has been observed. The mechanism of swelling of polymers in sc-CO2 and the overall effects of sc-CO2 on the transport properties of both small and large molecules has been studied. We report on the swelling characteristics of radi...