This study was directed toward the cationic polymerization of tetrahydroindene (i.e., bicyclo[4.3.0]-2,9-nonadiene), a bicyclic conjugated diene monomer, with a series of Lewis acids, especially focusing on the synthesis of high-molecular-weight polymers and subsequent hydrogenation for novel cycloolefin polymers with high service temperatures. EtAICl(2) or SnCl4 induced an efficient and quantitative cationic polymerization of tetrahydroindene to afford polymers with relatively high molecular weights (number-average molecular weight > 20,000) and 1,4-enchainment bicyclic main-chain structures. The subsequent hydrogenation of the obtained poly(tetrahydroindene) with p-toluenesulfonyl hydrazide resulted in a saturated alicyclic hydrocarbon polymer with a relatively high glass transition (glass-transition temperature = 220 degrees C) and improved pyrolysis temperature (10% weight loss at 480 degrees C). The new diene monomer was randomly copolymerized with cyclopentadiene at various feed ratios in the presence of EtAlCl2 to give novel cycloolefin copolymers, which were subsequently hydrogenated into alicyclic copolymers with variable glass-transition temperatures (70-220 degrees C). (c) 2006 Wiley Periodicals, Inc.