Preparation of a Bulky Cycloolefin/Ethylene Copolymer and Its Tensile Properties

Regioselective partial hydrogenation of tricyclopentadiene (TCPD) was achieved with a high turnover number of 10 000 by catalysis with a N-heterocyclic carbene−palladium complex. Copolymerization of ethylene and the partially hydrogenated product, dihydrotricyclopentadiene (HTCPD), was realized using a catalytic system of [8-(η 5 -C 5 Me 4 )-2-Me(C 9 H 8 N)-κ N ]TiMe 2 (C 9 H 10 NH = 1,2,3,4-tetrahydroquinoline) activated with (Ph 3 C) + [B(C 6 F 5 ) 4 ] − . The copolymer was unambiguously characterized through the analysis of one- and two-dimensional NMR spectra. The monomer reactivity ratios, r ethylene and r HTCPD, determined through the Fineman−Ross plot, were 2.8 and 0.025, respectively, indicating negligible successive insertion of two HTCPD. A nearly alternating copolymer with a HTCPD content of 45 mol % was obtained with a satisfactory activity (4.7 × 10 6 g/(mol Ti h)), of which T g was 177 °C, significantly higher than that of norbornene/ethylene copolymer at the same cycloolefin content. Tensile stress−strain curves indicated that the brittleness observed for a high- T g norbornene/ethylene copolymer was relieved to show some ductile property for the HTCPD/ethylene copolymer of the same level of high T g .