CO2 sorption in molten poly(E-caprolactone) (PCL) has been investigated by temporally resolved Raman line imaging, which is introduced here as a new technology for the direct measurement of gas mass fraction profiles inside polymers during transient sorption experiments. Molten PCL was exposed to pressurized carbon dioxide in an optically accessible pressure cell at 80 degrees C and pressures up to 7.1 MPa. During sorption, Raman spectra were acquired temporally and spatially resolved across the PCL drop, allowing the evaluation of the PCL/CO2 mutual diffusivity, of the CO2 solubility in PCL, and the determination of temporal evolution of mass fraction profiles of carbon dioxide inside PCL. (C) 2012 Elsevier Ltd. All rights reserved.