Pinene, a major constituent of pine tree oil, was cationically polymerized to generate a high-molecularweight polymer and then subsequently hydrogenated via metal catalysts to give a high-performance, biobased cycloolefin polymer with an alicyclic backbone. To obtain the high-molecular-weight polymer, the controlled/living cationic polymerization of (À)-b-pinene was investigated by an initiating system, consisting of a protonic acid, a Lewis acid, and an added base, along with an incremental monomer addition technique. Among the various systems, the RCl/EtAlCl 2 /Et 2 O system gave a high-molecularweight poly(b-pinene) (M w > 100 000). The catalytic hydrogenation of the obtained high-molecular-weight poly(b-pinene) was examined using various metal catalysts, among which Pd/Al 2 O 3 enabled the quantitative hydrogenation (>99.9%) of the unsaturated C]C group in the repeating unit under mild reaction conditions (1.0 MPa pressure of H 2 ). These reactions could be performed even at relatively large scales to produce several hundred grams of the polymer, which can be then processed through injection-molding. The synthesized bio-based cycloolefin polymers demonstrated promising potential properties as high performance optical plastics with good processability, low density, high optical transparency, low birefringence, non-hygroscopicity, high mechanical strength, and excellent thermal properties.

This paper reports a novel and practical method for the synthesis of styrene-isoprene-derived cycloolefin copolymer analogues via the intramolecular Friedel−Crafts alkylation of well-defined random copolymers of styrene and isoprene prepared by living anionic copolymerization in the presence of a small amount of tetrahydrofuran as a randomizer. The random copolymers with an almost equimolar amount of the two monomers (styrene:isoprene = 48:52) and a predominant 1,4-isoprene-enchainment (1,4-:1,2-:3,4- = 67:1:32) were intramolecularly cyclized with CF3SO3H efficiently to give the soluble cycloolefin copolymer analogues with a high glass transition temperature (T g). The T g increased dramatically (T g = 20 vs 130 °C) on cyclization between the aromatic ring of the styrene unit and the adjacent CC bond in the isoprene unit via the intramolecular Friedel−Crafts alkylation that results in the tetrahydronaphtyl bicyclic unit in the backbone chain, for which the highest T g was observed at the equimolar content of isoprene and styrene. The predominant Friedel−Crafts cyclization between the styrene and the adjacent isoprene units was supported by the model reactions of the corresponding low molecular weight model compounds.

Rubbery random copolymers of styrenes and dienes prepared via anionic living polymerizations were intramolecularly cyclized into high-performance thermoplastics.