Dihydroxytelechelic copolyalkenamers were prepared via metathetical polymerization of cyclic olefins (cyclooctadiene, cyclooctene and cyclododecene) in presence of first generation Grubbs catalyst and butene diacetate as functionalizing chain transfer agent in order to study their aging resistance. The influence of compositions and molar masses of the copolyalkenamers were investigated in terms of thermo-mechanical properties. Increasing chains length or the proportion of polycyclooctadiene allow to get non-cristalline polymers. Low T-g materials (between -78 degrees C and -108 degrees C) were prepared. The resistance towards oxidation of the different copolyalkenamers was carried out using a viscosity measurement method. A critical time, corresponding to a brutal increase of the apparent viscosity, was related to degradation of the polymers and was shown to be dependent on the Csp(2) proportion in the structure. The absence of vinylic units and the decrease of the double bonds content within the copolymers were proved to enhance the stability of the copolyalkenamers towards aging resistance. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1830-1836, 2010