Controlled Copolymerization of Ethylene and Biosourced Comonomers Using Dibenzobarrelene-Based α-Diimine Nickel...

The development of earth-abundant nickel-based catalysts is currently one of the greatest challenges for the straightforward synthesis of functionalized polyolefins. With environmental protection concerns, controllable copolymerizations of ethylene with biosourced comonomers derived from castor oil, such as methyl 10-undecenoate (U-COOMe), 10-undecen-1-ol (U-OH), or 10-undecenyl bromide (U-Br), were realized using α-diimine nickel catalyst (Ni-DBB) with dibenzobarrelene backbone. Catalyst Ni-DBB was highly tolerant toward polar comonomers, and functional polyethylenes were successfully prepared. The influences of the polar group, temperature, and comonomer concentration were studied in detail. Catalyst Ni-DBB was able to catalyze the copolymerization of ethylene with U-OH to afford high-molecular-weight (~180 kg/mol) functional polyethylene in a controlled fashion. NMR analysis showed that the produced functional polyethylenes were highly branched and had broad melting peaks ranging from 0 to 30 °C. Water contact angle (WCA) measurements showed that the surface of the obtained hydroxyl-functionalized polyethylene changed from hydrophobic to hydrophilic with the introduction of the comonomer U-OH.