A hydrogenated ring-opening polymer of a norbornene-based monomer such as dicyclopentadiene is a type of so-called cycloolefin polymer that exhibits excellent transparency, low birefringence, forming processability and the like, and thus is used as a material that can be applied to various applications such as optical applications.
A hydrogenated ring-opening polymer of dicyclopentadiene is normally obtained in the form of an amorphous polymer that has an atactic structure. However, the amorphous hydrogenated ring-opening polymer of dicyclopentadiene having the atactic structure may exhibit insufficient heat resistance, mechanical strength, solvent resistance and the like depending on the application. Hence, as a measure for improving the performance of such a hydrogenated ring-opening polymer, a hydrogenated ring-opening polymer of dicyclopentadiene that has crystallinity by producing a hydrogenated ring-opening polymer of dicyclopentadiene having a tactic structure on its main chain has been proposed.
For example, Patent Literature 1 discloses that a dicyclopentadiene ring-opening polymer having cis-syndio regularity that is soluble in a hydrocarbon solvent such as a cyclohexane at room temperature is obtained by subjecting dicyclopentadiene to ring-opening polymerization through the use of a polymerization catalyst that mainly includes a group 6 transition metal compound having a specific substituent such as a phenylimidotungsten tetrachloride diethyl ether complex, and furthermore a hydrogenated syndiotactic crystalline dicyclopentadiene ring-opening polymer having crystallinity is obtained by hydrogenating the carbon-carbon double bonds included in the ring-opening polymer through the use of a mixture of a bis(tricyclohexylphosphine)benzylideneruthenium(IV) dichloride and ethyl vinyl ether or the like, as a hydrogenation catalyst. In addition, Patent Literature 2 discloses that a crystalline dicyclopentadiene ring-opening polymer having cis-iso regularity that is insoluble in a hydrocarbon solvent such as cyclohexane at room temperature is obtained by subjecting dicyclopentadiene to ring-opening polymerization through the use of a polymerization catalyst that mainly includes a group 4 to 6 transition metal compounds that include a specific aromatic dioxy group as a ligand such as a phenylimidotungsten bisphenolate complex, and a hydrogenated isotactic crystalline dicyclopentadiene ring-opening polymer having crystallinity is obtained by hydrogenating the carbon-carbon double bonds included in the ring-opening polymer through the use of RuHCl(CO)(PPh3)2 or the like as a hydrogenation catalyst.