Synthesis of Thermo-Controlled Cyclic Olefin Polymers via Ring Opening Metathesis Polymerization: Effect of Copolymerization with Flexible Modifier

Cyclic olefin polymers (COPs) have gained attention as key components of future engineering plastics. Herein, we synthesized thermally stable COPs with high flexibility and optical transparency utilizing an industrially available WCl₆/iBu₃Al/EtOH catalyst system. The strategically designed cyclic monomers with flexible butyl group (nbutylnorbornene (nBuNB) and nbutyl-tetracyclododec-4-ene (nBuDMON) (flexible modifier)) and commercially available tetracyclic monomer (DMON) were copolymerized via ring opening metathesis polymerization (ROMP). Thereafter, the double bonds of the resulting polymer backbone were saturated by hydrogenation. The obtained series of COPs by changing the molar ratio of DMON and the flexible modifier showed not only various glass transition temperatures (T_g) ranged from 80 to 155 °C but also constantly high degradation temperatures (T_d,5%) around 300 °C. The representative hydrogenated P(DMON_0.7-co-nBuDMON_0.3) exhibited 155 °C of T_g and 402 °C of T_d,5% as well as excellent optical transmittance (> 91%) in the visible range. Considering these superior thermal stability, optical transparency, and high productivity (190 g L⁻¹), COPs with the flexible modifier were anticipated to be key component materials for future optical applications.[Figure not available: see fulltext.]