Identification of a Transient but Key Motif in the Living Coordinative Chain Transfer Cyclocopolymerization of Ethylene with Butadiene

Abstract

Copolymers of ethylene and butadiene were prepared using the ansa-bisfluorenyl Me2Si(C13H8)2NdR complex in combination with dialkylmagnesium as a chain transfer agent. Thorough kinetic studies and computational mechanistic investigations of this copolymerization reaction were performed. Combined with detailed analyses of the polymer microstructure and chainends, these studies demonstrate that the entitled copolymerization operates according to a living coordinative chain transfer copolymerization of ethylene and butadiene. Besides, in addition to the formation of the previously described 1,2-cyclohexane inner chain cyclic motif, the presence of bicyclic 1,5-decalin units via the formation of transient vinylcyclohexyl-methyl chain-end is discussed in the present communication. The non-accumulation of the vinylcyclohexane motif within the chains is explained by the reversibility of its formation, as interpreted with the help of DFT calculations, or by its rapid conversion into decalin motif after one ethylene insertion. Finally, this study also illustrates the ability of the fluorenyl ligand to adjust its binding mode on demand in order to avoid inhibition of catalyst.

Switch from Anionic Polymerization to Coordinative Chain Transfer Polymerization: A Valuable Strategy to Make Olefin Block Copolymers

“…[31] The resulting copolymers indeed feature ethylene units, trans-1,4 and 1,2 butadiene units and cyclohexyl moieties formed via an intramolecular cyclization mechanism. [31,32] This peculiar microstructure leads to original properties and the development of a new class of poly(ethylene-co-butadiene) rubber called ethylene butadiene rubber (EBR).…”

Design of selective divalent chain transfer agents for coordinative chain transfer polymerization of ethylene and its copolymerization with butadiene

“…Polymerization of ethylene or its copolymerization with butadiene mediated by this catalytic system have been shown to obey to a coordinative chain transfer (co)polymerization (CCT(co)P) (Scheme 2). 15,16 Scheme 2 General mechanism of coordinative chain transfer polymerization (CCTP) of olefins. M' is a main group metal or zinc As a controlled polymerization technique, CCTP potentially allows the production of end-functional polyolefins, [17][18][19] telechelic polyethylenes, 20,21 and block copolymers.…”

“…Polymerization of ethylene or its copolymerization with butadiene mediated by this catalytic system have been shown to obey to a coordinative chain transfer (co)polymerization (CCT(co)P) (Scheme 2). 15,16…”

“…Polymerization of ethylene or its copolymerization with butadiene mediated by this catalytic system have been shown to obey to a coordinative chain transfer (co)polymerization (CCT(co)P) (Scheme 2). 15,16 As a controlled polymerization technique, CCTP potentially allows the production of end-functional polyolefins, [17][18][19] telechelic polyethylenes, 20,21 and block copolymers. [22][23][24][25][26][27] Employing a polymetalated CTA based on zinc, Lee and coll.…”

High-Performance Elastomer from Trans-1,4 Copolymerization of Ethylene and Butadiene

“…However, copolymerizing the two monomers is rather difficult because of their different intrinsic polymerization activities and mechanisms. Since the discovery of Ziegler–Natta catalysts, attempts to copolymerize olefins and conjugated dienes have never been ceased, whereas only few transition-metal catalysts show high activity. − BD insertion into the polyethylene backbone forms cis-1,4, trans-1,4 and 1,2-configurations, of which cis-1,4-BD units in random distribution is highly expected. The resultant copolymers are a new type of rubbers possessing both tough and flexible properties; however, only two examples are reported to give cis-1,4-regulated E/BD copolymers.…”