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 (T _g) = 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 T _g (for both aromatic and cycloaliphatic side groups), whereas saturation of the side groups produces a 14°C increase in T _g (for both saturated and unsaturated backbones).