高温稳定的双层板型双核烯烃聚合催化剂设计合成及其协同作用研究

Introduction of polar groups could greatly improve the properties of polyolefins, such as adhesion, processibility, as well as compatibility with other polymers and assistants. Modification by direct copolymerization of olefins with polar comonomer is considered as the most facile and economic method, which is limited by the tolerance and stability of the catalysts. Although the double-decker-type dinuclear α-diimine nickel and palladium catalysts with obvious cooperative effects could efficiently copolymerize ethylene with polar monomers, they exhibited poor catalytic performance at elevated temperature. This project focuses on the design and synthesis of a type of novel double-decker-type dinuclear α-diimine nickel and palladium catalysts bearing 5,7,12,14-tetrahydro-5,14;7,12-diethanopentacene backbone to realize highly efficient copolymerization of ethylene with polar monomer. Because of the constrained effects of the backbone, the two metal centers of the dinuclear α-diimine nickel and palladium catalysts will occupy at the position closely to each other, and the cooperative effects during the polymerization would be enhanced. Moreover, compared with the catalysts reported in the scientific literatures, the steric hindrance of the catalysts designed in this project will be enhanced and their N-aryl groups could be varied more facilely. Therefore, their performances under elevated polymerization temperature could be further improved. The mechanism of cooperative effect during the copolymerizations will also be investigated in this project. A series of double-decker-type dinuclear α-diimine nickel and palladium catalysts with outstanding catalytic properties will be synthesized to copolymerize ethylene with polar monomer, and copolymers with excellent performance will be prepared.

在聚烯烃中引入极性基团，可有效改善其应用性能，意义十分重大。普遍认为直接共聚法最为简单、经济，但其实施过程往往受到催化剂耐受性和稳定性的限制。具有协同作用的双层板型双核镍、钯催化剂在常温下可高效催化乙烯与极性单体共聚，但其热稳定性却不尽理想。本项目以乙烯与极性单体共聚为研究对象，设计合成新型的双层板型双核α-二亚胺镍、钯催化剂，利用刚性的二乙撑基并五苯骨架将两个金属中心限定在相距较近的位置，提高双核催化剂在聚合过程中的协同作用，削弱极性单体对金属中心的“毒化”。另外，与文献报道的催化剂相比，本项目所设计的催化剂中配体骨架与N-芳基之间具有明显的位阻排斥效应，且N-芳基的位阻和电子特性灵活可调，能够实现对双核催化剂高温催化性能的进一步改善。在此基础上，本项目还将对双核催化剂协同作用机理进行研究，设计合成出性能优异的催化剂，并制备出高分子量、高极性单体含量的乙烯共聚物。

聚烯烃是全球年产量和年消耗量最大的高分子材料，广泛应用于民用、医用、工业等领域。目前我国聚烯烃产业集成化较低，高端聚烯烃产品主要依赖于进口。催化剂是调控聚烯烃结构和性能的决定性因素，本项目主要集中于具有优异热稳定性、极性基团耐受性和高活性的烯烃聚合催化剂的开发以及功能化聚烯烃材料的合成。本项目研究工作中，主要利用五蝶烯骨架，成功构筑了用于双核催化剂合成双层板型骨架；制备了不对称结构的α-二亚胺镍催化剂，并催化了降冰片烯聚合以及降冰片烯与极性单体的共聚，制备出了高分子量（35.4-1891 kDa）和极性单体含量为0.8-6.4 mol%的功能化聚烯烃；设计合成了具有环状骨架的钒催化剂，催化了乙烯聚合以及乙烯与降冰片烯衍生物的共聚，以极高的活性（>10 kgpolymer/mmolV·h）制备出了高分子量（43.1-344 kDa）、高共单体含量（2.77-40.6 mol%）的功能化环烯烃共聚物。本项目还利用双组份催化体系催化乙烯聚合，制备出了长链支化的聚乙烯，通过改变催化剂配比可以实现长链支化聚乙烯支化度在0.84-3.95 mol%范围内可调。与高密度聚乙烯相比，长链支化聚乙烯具有更为优异的流变性能和力学性能；此外，本项目还利用Ru催化剂催化了环辛烯与5-降冰片烯-2羧酸甲酯的共聚，通过次序加料法制备了两嵌段的极性环烯烃共聚物。通过改变单体投料比，实现了聚-5-降冰片烯-2羧酸甲酯嵌段聚合度在50-900范围内的调控。聚-5-降冰片烯-2羧酸甲酯嵌段长度对相应聚合物/碳纳米管杂环串晶的形貌及表面性能影响显著，经过工艺优化成功制备出了水接触角大于150°的超疏水材料。