Copolymerizations of ethylene and tricyclopentadiene (TCPD) are realized without formation of a gel with a high activity (3-18 x 10(6) g/molZr.h) using a catalytic system of [Ph2C(Flu)(Cp)]ZrCl2/MMAO. The monomer reactivity ratios, r(ethylene) and r(TCPD), determined through the Fineman-Ross plot, are 6.4 and 0.044, respectively, indicating that TCPD insertion is unfavorable, negligibly allowing the successive TCPD insertions. A significant higher glass transition temperature (T-g) is attained than those observed for other reported cycloolefin copolymers at the same cycloolefin content. A T-g as high as 214 degrees C is attainable at 41 mol % TCPD content. The remaining double bond can be hydrogenated to saturated hydrocarbon or converted to an epoxide group. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 938-944, 2011