Synthesis of multiblock ethylene/long‐chain α‐olefin copolymer via chain walking polymerization using thermostable α‐diimine nickel catalyst

Abstract

INTRODUCTIONIn recent years, there has been an explosion of research committed to the olefin block copolymers with diverse microstructures. Melting temperatures, glass transition temperatures, and mechanical properties of materials can be altered, when alkyl branches were introduced into carbon hydrogen backbone. 1 This was attributed to the reduction of main chain crystallinity by the alkyl branches. Brookhart et al. demonstrated that some late transition metal catalysts bearing bulky a-diimine ligand exhibited high activities in ethylene polymerization and copolymerization with comonomers, resulting in formation of different branches in the polymer chain. 2-4 Later, more palladium and nickel catalysts were developed and applied to a variety of applications areas. 5-7 These days, some researchers concentrated on new kinds of Ni(II) and Pd(II) complexes, such as dinuclear catalysts, and made astounding advances, 8,9 suggesting a tremendous potential in polymerizing materials with diverse microstructures. With the advantage of the unique chain walking feature of Brookhart-type catalysts, block polymer bearing both plasticity and elasticity can be designed, as the main point is to introduce crystalline or semicrystalline blocks into the amorphous chain segments. Xiao et al. reported a new multiblock polyethylene via chain shuttling polymerization of ethylene between a Brookhart-type catalyst and a bridged zirconocene, where the bridged zirconocene produced linear polyethylene segments. 10 Chen et al. addressed a series of a-diimine Ni(II) and Pd(II) catalyst with different substituents in ethylene (co)polymerization to control the polymer topology. 11-15 Some other researchers concentrated on utilizing the highly x,1-enchainment behavior (chain walking of

Chain-Straightening Polymerization of Olefins to Form Polar Functionalized Semicrystalline Polyethylene

“…In the late 1990s, Brookhart and co-workers reported cationic late-transition metal α-diimine complexes [ 1 (Figure )] for the polymerization of olefins. − Since this initial disclosure, the α-diimine ligand framework has permitted tuning of the polyolefin microstructure, − functionality, − topology, − and properties. − The versatility of this reaction platform is facilitated by the unique “chain-walking” behavior of these catalysts, which may be modulated by the choice of metal and the substituents on the α-diimine nitrogens and backbone . Chain-walking comprises consecutive β - hydride elimination and re-insertion of the metal center with opposite regiochemistry along the polymer backbone (see Table ).…”

Peroxide-Mediated Alkyl–Alkyl Coupling of Dialkylzinc: A Useful Tool for Synthesis of ABA-Type Olefin Triblock Copolymers

“…Furthermore, it was demonstrated that the novel C­(sp 3 )–C­(sp 3 ) coupling reaction could be utilized for the construction of valuable ABA-type polyolefin triblock copolymers, which are expected to exhibit useful thermoplastic elastomer properties (Scheme ). − Typically, the number-average molecular weight ( M n ) attainable in CCTP is limited (∼60 kDa). This work provides a method to prepare high molecular weight POs in CCTP and overcoming this limitation.…”