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. EtAlCl2 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 °C) and improved pyrolysis temperature (10% weight loss at 480 °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 °C). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6214–6225, 2006

The living cationic polymerization of a novel bicyclic conjugated diene monomer, tetrahydroindene (THI) (bicyclo[4.3.0]-2,9-nonadiene), was achieved using the SnCl 4 -based initiating system, in which the Lewis acid works as an activator for the dormant C-Cl terminal originating from the hydrogen chloride adduct of the 2-chloroethyl vinyl ether as an initiator (1) in the presence of a nucleophilic additive such as ethyl acetate. The number-average molecular weights of the obtained polymers increased in direct proportion to the monomer conversion, and the MWDs were narrow throughout the reactions (M w /M n ∼ 1.2). The well-defined terminal structure of the obtained poly(THI) was confirmed by the 1 H NMR and MALDI-TOF MS analysis, which shows the presence of the initiator moiety at the R end and the chlorine at the ω end. The living cationic block copolymerization of isobutyl vinyl ether (IBVE) followed by THI led to the di-and triblock copolymers consisting of the hard nonpolar THI and soft polar IBVE segments for possible application of the triblock copolymer as a thermoplastic elastomer.