Chemical Recycling and Upcycling of Functionalized Cyclic Olefin Copolymers

Cyclic olefin copolymers (COCs) have attracted significant interest as high-performance optical materials owing to their excellent transparency, low birefringence, and superior thermal stability. However, the rigid bicyclic structure of norbornene-derived monomers results in a high glass transition temperature (T_g), which limits thermal reprocessing and presents challenges for sustainable recycling. To address these limitations, ketone-functionalized gradient COCs were synthesized via controlled vinyl-addition polymerization and subsequently modified through post-polymerization functionalization to tailor their thermal and optical properties. Incorporation of siloxane-containing functionalities effectively reduced the T_g while preserving the outstanding optical transparency of the polymers, demonstrating that the thermal processability of COCs can be improved without compromising their optical performance. Furthermore, hydrolysis of the introduced functionalities regenerated hydroxyl groups, providing versatile reactive sites for subsequent chemical transformations and post-polymerization modification. This reversible functional group conversion enables not only chemical recycling of the polymer but also upcycling into value-added functional materials with tunable properties. The developed approach demonstrates a versatile platform for designing recyclable and reconfigurable COCs and highlights the potential of post-polymerization functionalization as a sustainable strategy for extending the lifecycle of advanced optical polymer materials.