二亚胺镍配合物催化乙烯聚合制备高性能线性低密度聚乙烯

Linear low density polyethylene (LLDPE) is a type of polymeric materials with superior comprehensive properties. Ethylene polymerization catalyzed by diimine ligated nickel complexes is an emerging methodology in LLDPE formation. The existing diimine ligated nickel catalytic systems, in most cases, inevitably suffer from issues of excessively broad product distribution, low catalytic activity at elevated temperatures, insufficient molecular weights, and severe lack of longer branches in the resultant LLDPE. These shortcomings in all disfavor diimine ligated nickel complex catalysts in the formation of high performance LLDPE. This project, therefore, focuses on the synthesis of diimine ligated nickel complexes which help them overcome the as-described disadvantages by designing and synthesizing rigid mononuclear diimine ligated nickel complexes with circular and semicircular configurations and bimetallic synergetic effects oriented dinuclear diimine ligated nickel complexes with commercial values. The introduction of varying substituents into the ligands' backbone tunes the steric hindrance and electronic effect of the ligands, thus influencing the chemical enviroment around nickel active sites and regulating nickel centers' "chain walking" behavior, catalyzing ethylene polymerization to obtain LLDPE with significantly increased molecular weights and long branches' percentage. MANCC method, the combination of molecular mechanics and QEq charge distribution, will be applied to explore the effects of the type of ligands and the variety of their substituents on the catalytic activities, thus establishing qualitative or quantitative relationship between the structure of diimine ligated nickel catalysts and their polymerization activities and affording theoretical guidance to the design of target nickel complexes. This project is highly expected in simitaneous dealing with the most concerned issues in diimine ligated nickel complex catalyts related LLDPE formation at elevated polymerization temperatures. Upon completion of this project, highly efficient diimine ligated nickel complex catalytic systems complying with the need for high operating temperatures in modern polyolefin industry and being capable of producing tailor-made LLDPEs will be developed.

线性低密度聚乙烯（LLDPE）是一类综合性能优异的高分子材料。二亚胺镍配合物催化乙烯聚合是一种新兴的LLDPE制备方法。现有二亚胺镍催化剂普遍存在乙烯聚合产物区分度差、高温活性低、分子量低、长支链含量少的不足，难以合成高性能LLDPE。本研究着眼于设计合成热稳定性好，乙烯聚合活性高、分子量及支链调控灵便的二亚胺镍配合物，以获得具有应用前景的高效环状、半环结构的刚性单核二亚胺镍配合物和具有协同效应的双核二亚胺镍配合物催化剂体系。通过改变配体的空间与电子效应影响镍活性中心的化学环境，调控中心金属的"链行走"，制备分子量高、长支链多的LLDPE。用分子力学与QEq电荷平衡相结合的MANCC方法考察配体骨架及其取代基对催化活性的影响，得到催化剂分子结构与催化活性之间定性或定量的关系，获得二亚胺镍催化剂调控规律及其理论解释。形成适合现代聚烯烃工艺要求、能制备高性能LLDPE的高效二亚胺镍催化体系。

线性低密度聚乙烯（LLDPE）主要通过乙烯与正烯烃共聚合成，而正烯烃的价格昂贵。二亚胺镍催化剂通过“链行走”作用，催化乙烯一种单体就能合成LLDPE。对称二亚胺镍催化剂多数有高温失活、PE分子量（MW）低与长支链量少等不足，限制了其在高端领域的应用。本研究通过改变配体的空间与电子效应，设计合成出多系列新型不对称二亚胺镍配合物，其高温下催化乙烯聚合性能优异，重要结果与关键数据如下：.1..设计合成系列1-[2,6-二(二苯甲基)-4-氟苯胺基]-2-芳基亚胺苊亚胺镍配合物，其在甲基铝氧烷（MAO）的作用下，30℃时催化活性高达12700 kg PE/(mol Ni h)，MW达1620 kg/mol，典型样品支化度为202 Me/1000C。.2..设计合成系列1-[2,4-二(二苯甲基)-6-氯苯胺基]-2-芳基亚胺苊亚胺镍配合物，其在倍半乙基氯化铝（EASC）作用下，50℃时催化活性达16500 kg PE/(mol Ni h)，80℃时仍达3760 kg PE/(mol Ni h)，典型样品的支化度为59 Me/1000C，其中长支链占45%。.3..设计合成系列1-(2,6-二(二(对氟苯基)甲基)-4-氟苯胺)-2-芳基胺苊二亚胺镍配合物，其在EASC作用下，30℃时催化活性达21950 kg PE/(mol Ni h)（70℃时为4220 kg PE/(mol Ni h)），典型样品的支化度为116 Me/1000C，其中长支链占41%。.4..设计合成系列1-(2,6-二(二(对氟苯基)甲基)-4-甲基苯胺)-2-(芳基胺)苊二亚胺镍配合物，其在MAO或Et2AlCl活化下，30℃时催化活性在10000 kg PE/(mol Ni h)以上，MW在100 kg/mol以上，典型样品的支化度大于100 Me/1000C。.5..设计合成系列1-(2,4,6-三(二苯甲基)苯胺)-2-芳基胺苊二亚胺镍配合物，其在Me2AlCl活化下，90℃时催化活性仍达2970 kg PE/(mol Ni h)，典型样品支化度为125-135 Me/1000C。聚合物具有较高拉伸强度和良好弹性。.6..设计合成系列6,6-二甲基-7-芳亚胺环戊烯并吡啶氯化镍配合物，其在MAO作用下，20℃时活性达5020 kg PE/(mol Ni h)，聚乙烯含不饱和端基。