Poly(phenylnorbornene) from Ring‐Opening Metathesis and Its Hydrogenated Derivatives

Novel polymers are synthesized from 5‐phenyl‐2‐norbornene (PhNb) and its saturated side group analog, 5‐cyclohexyl‐2‐norbornene, using ring‐opening metathesis polymerization (ROMP). Polymers of both endo‐rich and all‐exo PhNb show glass transition temperatures (Tg) = 88 ± 1 °C, indicating a negligible effect of monomer stereoisomerism on segmental packing or the energy barriers to motion at the glass transition, despite the substantial size of the side group. Post‐polymerization hydrogenation of the PhNb polymers using catalysts with different selectivities reveals that saturation of the backbone produces a 17 °C decrease in Tg (for both aromatic and cycloaliphatic side groups), whereas saturation of the side groups produces a 14 °C increase in Tg (for both saturated and unsaturated backbones).