The Highly Controlled and Efficient Polymerization of Ethylene

Abstract

The highly controlled and efficient polymerization of ethylene is a very attractive but challenging target. Herein we report on a Coordinative Chain Transfer Polymerization catalyst, which combines a high degree of control and very high activity in ethylene oligo-or polymerization with extremely high chain transfer agent (triethylaluminum) to catalyst ratios (catalyst economy). Our Zr catalyst is long living and temperature stable. The chain length of the polyethylene products increases over time under constant ethylene feed or until a certain volume of ethylene is completely consumed to reach the expected molecular weight. Very high activities are observed if the catalyst elongates 60 000 or more alkyl chains and the polydispersity of the strictly linear polyethylene materials obtained are very low. The key for the combination of high control and efficiency seems to be a catalyst stabilized by only one strongly bound monoanionic N-ligand.

Coordinative Chain Transfer and Chain Shuttling Polymerization

“…Finally, among noteworthy results are an ethene CCG using an aluminum-based CTA with a guanidinate zirconium complex 2i and the selective Mg alkyl/mesityl CTA Vb where only the alkyl side initiates the chain transfer.…”

“…13 Catalyzed chain growth (CCG) of ethene with very high catalyst economy and aluminum based CTA was reported, using the zirconium catalytic complex 2i (Figure 1). 14 Zirconium complex 2i was activated by dimethylanilinium tetrakis(pentafluorophenyl)borate cocatalyst and in combination with Et 3 Al as CTA provided linear polyethylenes with a narrow molar mass distribution (Đ = 1.2). This catalytic system showed high activities and extremely efficient chain transfer (up to 60000 chains per Zr metal), which was ascribed to the structure of Zr complex 2i, stabilized by bulky guanidinate ligand.…”

“…This catalytic system showed high activities and extremely efficient chain transfer (up to 60000 chains per Zr metal), which was ascribed to the structure of Zr complex 2i, stabilized by bulky guanidinate ligand. 14 The classical Dow's hafnium pyridylamido CCTP catalyst bearing i-Pr substituents (3, Figure 2) was structurally modified (4, substituents R and R 1 , Figure 2) and tested for ethene CCTP and its CCTcoP with propene in order to avoid the deactivation of the original catalyst that may occur during the CCTP process. 15 The R 1 isopropyl moiety affected not only the geometry (distorted vs planar for i-Pr) of complexes but also its catalytic behavior.…”

Trendbericht Anorganik 2024: Nebengruppen, Bioanorganik und Koordinationschemie

“…Dieser erlaubt, die Kettenlänge über die Ethylenmenge zu kontrollieren, bei gleichbleibend geringer Polydispersität der Polymere. 17) Im Fall von Palladium lösten Harth, Grabow und Mitarbeiter:innen ein Rätsel bei der Olefinpolymerisation durch Diiminkomplexe. 18) Bei dieser zeigte sich eine ungewollte Isomerisierung zu internen Olefinen.…”

Efficient Preparation of Isotactic Polypropylene-Based Block Copolymers with Tunable Mechanical Properties: From Thermoplastics to Elastomers

“…To produce OBCs with higher efficiency and lower cost, a new polymerization method is highly expected. In this regard, coordinative chain transfer polymerization (CCTP), a quasi-living polymerization based on the reversible chain transfer between transition metal active species and main-group metal alkyls, has emerged as a solution to the low productivity of living polymerization. − CCTP is conceptually analogous to controlled radical polymerization with quasi-living characteristics, and it involves a dynamic equilibrium between active and dormant species. − An efficient CCTP system relies on the proper combination of transition metal catalysts and main-group metal alkyls, with the latter often referred to as chain transfer agents (CTAs). With the introduction of CTAs, each active center can initiate dozens to thousands of polymer chains, overcoming the “one chain per metal” yield limitation of living polymerization. , Therefore, CCTP has become a practical solution for the large-scale production of OBCs.…”