Direct Synthesis of Ultrahigh Molecular Weight Ethylene/Acrylate Copolymers Catalyzed by Binuclear Ni catalytic System

The non-polar nature of ultrahigh molecular weight polyethylene (UHMWPE) inherently limits its high-end applications. Introducing polar functional groups into the polyethylene (PE) chain can enhance its surface and rheological properties, further increase product value and application fields. Development of efficient catalytic systems for the direct copolymerization of ethylene with polar monomers remains a significant challenge in achieving high MW functionalized PE. To address this challenge, we synthesized two novel binuclear o -phosphinophenolate Ni(II) complexes (i.e. Me 2 C{C 6 H 2 -3-R- [5-P(C 6 H 3 -2,6-(OMe) 2 ]-4-O-Ni} 2 , R=9-carbazolyl, 1 ; R=4- n -butyl-2,3,5,6-tetrafluorophenyl, 4- n Bu-C 6 F 4 , 2 ) via modulating the steric and electronic properties of the phenol ring substituents. These binuclear o -phosphinophenolate Ni(II) complexes were employed in the coordination copolymerization of ethylene with acrylic monomers ( tert -butyl acrylate ( t BA), n -butyl acrylate ( n BA), methyl acrylate (MA), and methyl methacrylate (MMA)). It was observed that: 1) the binuclear o -phosphinophenolate Ni(II) catalytic system showed a characteristic single-component feature (cocatalyst/activator free); 2) complexes 1 and 2 produced highly linear UHMWPE and UHMW ethylene/acrylate copolymers; and 3) complex 1 catalyzed ethylene/ t BA copolymerization created a linear functionalized UHMWPE with t BA incorporation up to 2.83 mol%. Thus, the direct synthesis of polar functionalized PE with UHMW was successfully realized with the utilization of the binuclear o -phosphinophenolate Ni(II) complexes catalyzed ethylene-acrylates copolymerization under industrial relevant conditions.