All-Hydrocarbon High-Refractive-Index Cyclic Olefin Copolymer Optical Materials

High-refractive-index polymers are important materials in optoelectronics. Cyclic olefin copolymers (COCs) are among the most promising optical materials; however, high-refractive-index COCs still remain unsolved but are highly desired. In this study, principles for designing all-hydrocarbon high-refractive-index COCs were proposed. Diverse COCs were prepared by zirconium-catalyzed coordination–insertion copolymerization of nine types of aromatic group-containing cyclic olefins with ethylene. In all-hydrocarbon optical polymers, these COCs have significantly higher refractive indices of >1.60, >1.65, and >1.70 compared to the previous values at moderate cyclic olefin incorporation (maximum: 35.7 mol%) and are highly optically transparent (90%–94%) in the visible wavelength range. Furthermore, these COCs are amorphous, have a wide Tg range of 92–262 °C, exhibit high thermal stability (Td,5% = 372–442 °C), and possess extremely low hygroscopicity of <0.01%. These merits of all-hydrocarbon COCs indicate their potential as optical materials.