The synthesis of ethyl ene-co-5,7-dimethylocta-1,6-diene copolymers (CEDMO) with different molar DMO contents has been performed to incorporate double bonds in the lateral and make easier the development of crosslinkings in the resulting polymer material after application of electron-beam irradiation. The gel content as well as a comprehensive evaluation of the changes in the crystalline characteristics have been carried out. Both features are strongly dependent on DMO composition and irradiation closes. Variation in the mechanical response of the different specimens has been checked by microhardness measurements. (c) 2009 Elsevier Ltd. All rights reserved.