Copolymerization of ethylene with polar styrene monomers catalyzed by phosphino-dihydronaphtholate neutral nickel catalysts

The physical properties of traditional polyolefin materials can be significantly improved by introducing polar groups, especially polar aromatic groups. However, it remains a major challenge to realize the highly effective copolymerization of ethylene with styrene derivatives. In this study, the direct copolymerization of ethylene with various polar styrene monomers bearing functional groups (o-OMe, m-OMe, p-OMe, o-Cl, m-Cl, p-ClSt, o-F, o-Br, p-Me, p-Ph, p-Vinyl, p-COOH, and C6F5) was achieved using phosphino-dihydronaphtholate neutral nickel catalysts Ni1-Ni3. Additionally, the catalytic behavior and the applicability of the polar monomer were evaluated in detail by copolymerization results. Catalysts Ni1-Ni3 demonstrated inactivity towards the polymerization of polar styrene monomers but exhibited moderate catalytic activities in the copolymerization of ethylene with polar styrene monomers, yielding moderate-molecular-weight (M-w > 10 kDa) copolymers with the polar monomer contents ranging from 1.32 to 4.16 mol%. The steric and electronic effects of the substituent depending on the types and position in the phenyl ring considerably influenced the copolymerization behavior. Furthermore, comprehensive NMR analyses of the produced copolymers revealed that the polar monomers formed in-chain insertions, saturated chain ends, and unsaturated chain ends after incorporation.