Films based on polyamide 6 were prepared by cast extrusion keeping all the extrusion parameters constant except the chill-roll temperature. The impact of the process conditions on the morphology and transport properties was investigated. The structure of the matrix crystalline phase and the molecular mobility of the polymer chain in the amorphous phase highly depended on the films processing conditions. The gas permeation properties and the water and ethanol sorption properties were determined and a detailed analysis of the sorption mechanism was proposed on the basis of thermodynamic and kinetic modeling. The transport mechanism was shown to result from a combination of different contributions involving the size of the permeant, the free-volume holes distribution and the amount of gamma phase in the crystalline part of the polymer. This study underlined also the potentiality of using molecules differing in their size as an original way to probe the architecture of these systems. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.