串级催化聚合制备线性低密度聚乙烯/聚烯烃热塑性弹性体

通过齐聚催化剂和共聚催化剂的有机结合和相互协同，可实现以乙烯为唯一单体的串级催化聚合，合成乙烯与α-烯烃共聚的线性低密度聚乙烯和聚烯烃热塑性弹性体，但开发高选择性、高共聚能力、适合高温聚合的串级聚合催化体系仍极具挑战。本文围绕不同类型的乙烯齐聚/聚合反应，评述了乙烯二聚、三聚、四聚及聚烯烃大单体合成技术及其相应的串级催化聚合的研究进展。迄今，大部分串级催化聚合是在较低的聚合反应温度下进行的，有限的串级催化体系适合高温聚合；乙烯二聚和三聚串级催化聚合可合成短支链较均一的乙烯与α-烯烃共聚物，但在乙烯四聚串级催化聚合中1-辛烯的选择性亟待提高；此外，通过聚烯烃大单体的串级催化聚合，可为具有特殊链拓扑结构的高性能聚烯烃热塑性弹性体的开发开拓新途径。

Preparation of linear low density polyethylenes/polyolefin thermoplastic elastomers by tandem polymerizations

The ethylene/α-olefin copolymers including linear low density polyethylene and polyolefin thermoplastic elastomer can be synthesized by a tandem polymerization with ethylene as only monomer, in the present of a combination of oligomerization and copolymerization catalysts as a tandem catalyst system. However, the development of tandem catalyst systems with high α-olefin selectivity and high copolymerization reactivity at high temperature still remains great challenging. Herein, the progress in the study of ethylene dimerization, trimerization, and tetramerization and polyolefin macromonomer synthesis, and their related tandem polymerizations are reviewed. Majority of tandem polymerizations have been carried out at low temperature. Very few tandem catalyst systems were suitable for polymerization at high temperature. Although ethylene/1-butene and ethylene/1-hexene copolymers could be produced by tandem polymerizations with high α-olefin selectivity in the oligomerization, 1-octene selectivity in the tandem polymerization with ethylene tetramerization should be enhanced. The incorporation of polyolefin macromonomers into polyolefin backbones via tandem polymerization offered alternative approach for developing high-performance polyolefin thermoplastic elastomers with special chain topology.