双核烯烃聚合催化剂的制备及其催化烯烃聚合行为

In order to obtain olefin polymerization catalysts with high catalytic activity, excellent structural controllability or copolymerization ability, various bimetallic catalysts will be synthesized. The cooperativity effects between two metal centers or the increased steric hindrance around the metal centers of binuclear catalysts will tune the chain growth and chain transfer reactions, which will be helpful to improve the catalyst performance. Bidentate phenoxy-phosphine ligands, phosphine oxide-bridged phenolato ligands and phosphine sulphur-bridged phenolato ligands will be obtained from naphthalenediol, biphenol, spirocyclic bisphenol and so on. New binuclear group IV half-metallocene complexes containing bi-[P,O] bi-[P=O,O] and bi-[P=S,O] ligands will be thus synthesized by reaction of CpMCl3 (M =Ti, Zr, Hf) with corresponding ligands. Novel binuclear hybrid non-metallocene group IV complexes will also be prepared by the combination of bi-salicylaldimine ligands and β-enaminoketonato ligands/phenoxy-phosphine ligands. In addition, binuclear neutral nickel(II) complexes will be achieved from bi(phenoxy-phosphine)ligands and various nickel sources. Furthermore, the polymerization mechanism and kinetics and density functional theory will be used to investigate the effect of the catalyst structures on polymerization behaviors. Empolying these novel group IV catalysts, the stereoselectivity polymerization of propylene and styrene, and the high efficiency regioselectivity copolymerization of ethylene and functional monomer are expected to be realized. Ethylene and polar monomer copolymerization will also be carried out using binuclear neutral nickel(II) catalysts due to their low electrophilicity and high tolerance of polar functional groups. High performance functional polyolefin materials would be thus prepared using these new binuclear complexes.

本项目拟通过双核化技术，即利用金属间的协同效应或金属中心增大了的立构效应来实现对链增长及链转移反应的调控，提高催化剂性能，获取高活性、高结构可控性或高共聚能力的新型烯烃聚合催化剂。以萘二酚、联苯二酚以及螺环双酚等为原料合成双(酚-膦)、双(酚-膦酰)、双(酚-膦硫酰)等配体，制备含有环戊二烯基配位的新型双核半茂第四族配合物；也可从联苯二酚以及螺环双酚出发，合成系列以水杨醛亚胺配体为骨架的双核杂配非茂钛烯烃聚合催化剂；还可利用上述双(酚-膦)配体合成新型双核中性镍催化剂。通过对聚合反应机理与动力学的研究以及基于密度泛函理论的分子模拟手段，获得催化剂结构对聚合反应的影响规律。利用优选的双核第四族烯烃聚合催化剂，实现丙烯等α-烯烃或苯乙烯的立构选择性聚合及乙烯与功能单体的区域选择性共聚合；利用低亲电性和强耐受极性官能团的单组分中性镍催化剂，实现乙烯与极性单体的高效共聚合，制备新型聚烯烃材料。

聚烯烃是世界上产量最大、应用最广泛的高分子材料。催化剂是聚烯烃工业的核心技术。现有研究表明，催化剂的性能不仅取决于中心金属，还取决于金属中心的配位环境，即配体的类型、电子和空间构型。因此寻找合适的配体，设计合成新型的过渡金属配合物使之适用于聚合反应所需的电子和空间结构，进一步改善催化剂的催化活性、高温热稳定性和高结构可控性，成为当前烯烃聚合催化剂研究的主要目标。.本项目通过双核化技术，即利用金属间的协同效应或金属中心增大了的立构效应来实现对链增长及链转移反应的调控，提高催化剂性能，获取新型烯烃聚合催化剂。例如，以9,9-二甲基氧杂蒽为原料，合成双核中性镍催化剂。与单核催化剂相比，双核催化剂催化乙烯聚合时表现出更高的活性，所得聚合物的分子量是单核的25倍，其热稳定性显著高于单核催化剂。这些结果表明，双核催化剂显著地抑制了链转移反应。此外，双核催化剂还可以催化乙烯与1,5-己二烯或1,7-辛二烯的共聚合，得到带有悬挂双键的聚合物，而单核催化剂对共聚没有活性。通过对聚合反应机理与动力学的研究以及基于密度泛函理论的分子模拟手段，获得催化剂结构对聚合反应的影响规律。 课题组也以二苯并呋喃为原料，合成与表征单核、双核二苯并呋喃 [N,O] 类型中性镍催化剂；合成出系列酯桥连单双核[N,O] 类型中性镍催化剂；也制备了双(酚-膦)钛催化剂。但这些双核催化剂催化乙烯聚合行为与单核催化剂差异不大，这可能是由于金属中心相距太远，没有形成协同作用。本课题还制备了含水杨醛亚胺配体双核烷基铝配合物，在苯甲醇的活化下，这些配合物都能在高温(70°C)下可催化剂己内酯(ε-CL)聚合。通过改变催化剂结构可有效调控催化活性、所得聚合物分子量及其分布。