(ⁿBuCp)₂ZrCl₂-catalyzed ethylene-4M1P copolymerization: Copolymer backbone structure, melt behavior, and crystallization

The judicious design of methylaluminoxane (MAO) anions expands the scope for developing industrial metallocene catalysts. Therefore, the effects of MAO anion design on the backbone structure, melt behavior, and crystallization of ethylene-4-methyl-1-pentene (E-4M1P) copolymer were investigated. Ethylene was homopolymerized, as well as copolymerized with 4M1P, using (1) MAO anion A (unsupported [MAOCl₂]^-) premixed with dehydroxylated silica, (ⁿBuCp)₂ZrCl₂, and Me₂SiCl₂; and (2) MAO anion B (Si-O-Me₂Si-[MAOCl₂]^-) supported with (ⁿBuCp)₂ZrCl₂ on Me₂SiCl₂-functionalized silica. Unsupported Me₂SiCl₂, opposite to the supported analogue, acted as a co-chain transfer agent with 4M1P. The modeling of polyethylene melting and crystallization kinetics, including critical crystallite stability, produced insightful results. This study especially illustrates how branched polyethylene can be prepared from ethylene alone using particularly one metallocene-MAO ion pair, and how a compound, that functionalizes silica as well as terminates the chain, can synthesize ethylene-α-olefin copolymers with novel structures. Hence, it unfolds prospective future research niches in polyethyne systhesis.