Living Coordinative Chain-Transfer Polymerization and Copolymerization of Ethene, α-Olefins, and α,ω-Nonconjugated Dienes using Dialkylzinc as “Surrogate” Chain-Growth Sites

Abstract

Highly efficient, rapid, and reversible chain transfer between active transition-metal-based propagating centers derived from {Cp*Hf(Me)[N(Et)C(Me)N(Et)]}[B(C6F5)4] (Cp* = η5-C5Me5) (1a) or {Cp*Hf(Me)[N(Et)C(Me)N(Et)]}[B(C6F5)3Me] (1b) and multiple equivalents of dialkylzinc (ZnR2) acting as “surrogate” chain-growth sites has been achieved for establishing the living coordinative chain-transfer polymerization (CCTP) of ethene, α-olefins, and α,ω-nonconjugated dienes and living CCTP copolymerization of ethene with α-olefins and α,ω-nonconjugated dienes. These living CCTP processes not only provide a work-around solution to the “one chain per metal” cap on product yield currently limiting traditional living coordination polymerization of ethene and α-olefins but, in addition, provide access to practical volumes of a variety of unique new classes of precision polyolefins of tunable molecular weights and very narrow polydispersity (M w/M n ≤ 1.1).

Living polymerization of olefins with ansa-dimethylsilylene(fluorenyl)(amido)dimethyltitanium-based catalysts

“…This kind of polymerization is referred to as coordinative chain transfer polymerization and the metal alkyls are referred to as chain-shuttling reagents. 71,72 A suitable combination of the catalysts, which differ in copolymerization ability, produced multiblock copolymers via the copolymerization of ethene with 1-octene in the presence of Et 2 Zn as a chain-shuttling reagent. The synthesis of a multiblock copolymer through this mechanism is called chain-shuttling polymerization.…”

Synthesis of a novel branched–hyperbranched diblock polyolefin via chain walking and chain transfer polymerization from ethylene alone

“…Therefore, highly efficient, rapid and reversible chain transfer between nickel-metal active centers and zinc-metal inactive centers ensures the possibility of chain growth rather than chain termination. [14][15][16][17][18] Based on the above development of catalyst and catalytic technology, [1] we adopted two steps by one pot to synthesize hyperbranched-branched diblock polyethylene under changing temperature conditions. First, CatA/ MAO/ZnEt 2 at 40°C and 1 atm ethylene pressure catalyzed ethylene polymerization to produce hyperbranched polyethylene via fast chain walking.…”

“…[11][12][13] Meanwhile, ZnEt 2 , as chain transfer agent, was added into catalyst system with the aim at facilitating the active growth chain transfer from metal active center to Zn metal atom at high temperature and reversible transfer from Zn metal atom to metal active center. [14][15][16][17][18] This strategy stands out from living polymerization and chain shuttling polymerization for just using ethylene in carrying out under different polymerization temperature and obtaining the resultant polymer with novel microstructure.…”

Efficient Synthesis of Aluminium‐Terminated Polyethylene by Means of Irreversible Coordinative Chain‐Transfer Polymerisation Using a Guanidinatotitanium Catalyst

“…Pioneering work that involved well‐defined molecular polymerisation catalysts was reported by Eisenberg and Samsel5,6 as well as Mortreux and co‐workers. Meanwhile, ethylene CCTP catalyst systems that use rare‐earth metals (RE) and transition metals (TM) in combination with different chain‐transfer agents (CTA) such as Mg‐,7–12 Zn‐,13–25 and Al‐5,6,26–39 alkyls, have been developed. Mechanistic studies have been carried out by the groups of Bochman40,41 and Norton 42,43.…”