Modular Control of Glass Transition and Transparency in ROMP-Derived Oxanorbornene Polymers

Abstract Achieving both high optical transparency and high glass-transition temperature (Tg) remains challenging in cyclic olefin polymers. Here, ring-opening metathesis polymerization (ROMP)-derived oxanorbornene polymers enable modular tuning of these competing properties through imide N-substitution and comonomer architecture. P-OCy exhibited a Tg of 224.5 °C with 94.9% transmittance at 400 nm. Flexible ester comonomers improved transparency but reduced Tg to 121.1–146.4 °C, whereas rigid MMETCD preserved Tg near 210 °C while increasing P-OPh transmittance from 61.0% to 90.0%. These systematic comparisons reveal distinct structural contributions to thermal rigidity and optical clarity, establishing practical design guidelines for transparent, high-Tg oxanorbornene polymers.