Copolymerization of norbornene (NB) and fluorene-containing alkene comonomers using the Me 2 Si(Flu)(N t Bu)-TiMe 2 complex as a catalyst was investigated. The copolymerization successfully proceeded at any monomer feed ratio in high activity and gave copolymers with various comonomer contents. The structure of these copolymers would be gradient because NB was preferentially consumed in a quasi-living polymerization system. Two relaxation processes at 100−150 and 270−300 °C in dynamic mechanical analysis, which show phase-separation of the copolymer, supported the formation of the gradient structure. The obtained copolymers showed a high refractive index as hydrocarbons and extremely low photoelasticity (<10 −11 Pa −1 ). For reducing the photoelasticity, a monomer design free from reactive tertiary carbons would be important.

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