Synthesis and Chemical Transformation of Nitrogen-Rich Polyolefins through Copolymerization of Ethylene with Polar Cyclic Olefins

Direct coordination–insertion copolymerization of ethylene with polar monomers provides an atom- and energy-efficient route to functionalized polyolefins. However, the incorporation of nitrogen-containing comonomers into polyolefins remains problematic due to nitrogen-induced catalyst poisoning. Herein, two highly strained bicyclic nitrogen-containing comonomers (aminooxy-embedded norbornene: NBNO, aza-embedded norbornene: NBNN) are introduced, which effectively diminish the catalyst poisoning propensity. The copolymerization of ethylene with NBNO results in the formation of poly(E-NBNO) with high comonomer incorporation of 38.3 mol %. Likewise, the reaction with NBNN produces poly(E-NBNN), which possesses both high molecular weight of 108.1 × 103 g mol–1 and high comonomer incorporation of 28.3 mol %. By adjusting the concentration of NBNN, the semicrystalline poly(E-NBNN) (Tm = 126–127 °C) is transformed into the amorphous, transparent, optical poly(E-NBNN) (Tg = 60–132 °C; transmittance = 95.2–96.6% at 400 nm). Notably, poly(E-NBNO) undergoes N–O reductive cleavage, giving bifunctional poly(E-NH–OH) that features both −OH and −NH moieties. Poly(E-NBNN) is transformed into an azo-containing polyolefin [poly(E-N═N)]. Precise modulation of the N2-extrusion conditions in poly(E-N═N) enables the formation of diverse all-hydrocarbon cyclo-containing polyolefin architectures, which are difficult to access by other methods. This work circumvents conventional nitrogen-induced deactivation and provides a versatile platform for the synthesis and transformation of nitrogen-functionalized polyolefins.