Catalytic cyclopropanation of commercial 1,2- or 1,4-cis-polybutadiene, respectively, with ethyl diazoacetate catalyzed by [Tp(Br3)Cu(NCMe)] (Tp(Br3) = hydrotris(3,4,5-tribromo-1-pyrazolyl)borate) at room temperature afforded high molecular weight (M-n > 10(5) mol(-1)) side-chain or main-chain, respectively, carboxyethyl cyclopropyl-substituted polymers with variable and controlled degrees of functionalization. Complete functionalization of 1,4-cis-polybutadiene afforded poly[ethylene-alt-(3-ethoxycar-bonyl-cyclopropene)]. Catalytic hydrogenation of residual double bonds of partially cyclopropanated polybutadienes provided access to the corresponding saturated polyolefins. Thermal properties are reported. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4439-4444, 2010