Dense films based on the hydrophobic Pebax® 2533 were prepared by using solution casting in different solvents as well as compression molding and subjected to photo–aging under ultraviolet (UV) irradiation. The influence of the preparation method, including the casting solvents, as well as the UV irradiation time selected to treat the samples, were evaluated in terms of permeation rates of pure gases (CO 2, N 2, O 2, CH 4, He, and H 2). The transport data were correlated with the microstructure and surface properties by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), as well as water contact angle measurements. The obtained results showed that a controlled photo-oxidation process reduces the hydrophobicity of the Pebax® 2533 films, increasing their permeability without compromising their integrity. View Full-Text