Progress in the catalyst for ethylene/α‐olefin copolymerization at high temperature

Abstract

Ethylene/α‐olefin copolymers are one of the most widely‐used polyolefin materials. With the continuous improvement of polyolefin catalysts, high‐performance polyolefin materials were synthesized by adjusting the chain microstructure, changing the comonomer type and comonomer insertion amount, among which the ethylene/α‐olefin random copolymer elastomer (POE) and olefin block copolymer elastomer (OBC) are the most famous and well accepted by the market. The excellent properties of POE and OBC first depend on their polymer chain microstructure. The chain microstructure of polyolefins is fundamentally determined by the catalysts, polymerization conditions, comonomer feed policies, and reaction engineering. High‐performance ethylene/α‐olefin copolymer elastomers are currently prepared by high‐temperature solution polymerization process, which needs to be carried out at a temperature above the melting point of the polymer and is beneficial to speed up the polymerization reaction rate and control the polyolefin chain microstructure. However, the high‐temperature solution polymerization process launched more stringent requirements for the olefin coordination polymerization catalyst. Systematic reports on catalysts for high‐temperature solution copolymerization of ethylene and α‐olefins are lacking. In this review, we screened some catalysts suitable for the controllable copolymerization and high‐temperature solution copolymerization of ethylene/α‐olefin based on the catalyst's heat resistance, copolymerization activity, comonomer insertion ability, molecular weight, and distribution of the copolymer, including traditional Z–N catalysts, metallocene catalysts, and post‐metallocene catalysts. And the future development of catalysts for high‐temperature solution copolymerization of olefins, catalysts for precise control of polyolefin chain microstructures, and catalysts for olefin copolymerization with polar monomers at high temperature are envisaged.

Recent progress in eutectic gallium indium (EGaIn): surface modification and applications

“…Due to its superior photothermal conversion efficiency and biosafety, liquid metals, a new form of biomaterial, provide more options for treating tumors. 166,184 The first consideration in the application of liquid metals in therapy is cytotoxicity, and liquid metals and their composites are non-toxic to the body, so they can be applied in tumor therapy. 226 In order to enter and function better in the human body, liquid metals need to be processed into droplets of a small diameter and be stable in the body and able to carry drugs, which requires surface modification of liquid metals.…”

Archie E. Hamielec memorial issue

“…The authors of the articles in this issue join us from many countries and institutions across the globe (Figure 1 and Table 1) to thank Archie for his enduring legacy in polymerization reaction engineering, a field of academic and industrial interest that he established practically single‐handedly. [ 1–45 ]…”

Unveiling the mutual effects of hydroxyl and dibenzhydryl groups in α‐diimino‐nickel precatalysts for direct synthesis of polyethylene elastomers

“…These catalysts can produce polyolefins with both short‐ and long‐chain branches along the polymer chain, and the specific nature of these branches depends on the particular type of α‐olefin used in copolymerization with ethylene. The density and distribution of these branches are closely associated with the material properties of POE; therefore, imprecise control of comonomer ratio can result in the production of polymers with less efficient material properties 7 . Moving forward, in the mid‐1990s, the ground breaking discovery of α‐diimino‐nickel and ‐palladium precatalysts sparked a renaissance in catalytic olefin polymerization (Figure 1a).…”

“…The nickel catalysts demonstrated high catalytic efficiency at lower reaction temperatures. However, they are unsuitable for the prevailing industrial condition of higher temperatures required for solution‐based polymerization processes, because they yield low molecular weight polyethylene and inferior mechanical properties at elevated temperatures 7 . Thus, the challenge remains to enhance catalytic performance without compromising the quality of the polyethylene produced at elevated temperatures.…”