Application Of Tert-butyl Strategy In Olefin Homogeneous Polymerization And Copolymerization

Polyolefin is one of the most widely used polymer materials in the world.As one of the countries with the largest consumption,China has a great industrial production capacity of polyolefin.But the productions are mainly low-end products which are used in packaging,daily chemicals and et al.At the same time,high-end polyolefins,such as polyolefin elastomers and cycloolefin copolymers,are relied heavily on imports.The production technologies of high-end polyolefins have been monopolized and blocked by European,American and Japanese companies for a long time,which has become a veritable "bottleneck" problem.Therefore,it is of great strategic significance to develop new polyolefin catalytic systems and polyolefin strategies.Homogeneous polymerization catalysts have single active center,so the polymer products have narrow molecular weight distribution and controllable microstructure,which have been used in the production of high-end polyolefins.However,in the existing studies,the high catalytic activity of homogeneous polymerization catalysts is usually obtained in aromatic solvents,such as toluene,rather than in saturated aliphatic hydrocarbon solvents.One of the main reasons is that the solubility of the catalytic system in saturated aliphatic hydrocarbon solvents is poor.In view of the fact that saturated aliphatic hydrocarbon solvents are generally used for polymerization in the polyolefin industry,the design and synthesis of new homogeneous catalysts and cocatalysts with high solubility become the key to solve this problem.The main idea of this project is to design new primary catalysts and cocatalysts by adding tert-butyl to the structure,which can make the catalytic system have good polymerization effect in the homogeneous catalytic system by improving its solubility,as follows:1.First,we synthesized a large sterically hindered aniline containing multiple tertbutyls,and using this aniline to synthesize a variety of nickel catalysts with different skeleton structures.The presence of multiple tert-butyls can significantly improve the solubility of the catalyst,and its polymerization activity in saturated aliphatic hydrocarbon solvents solvent can be equivalent to that in aromatic solvents,while the corresponding nickel catalyst without tert-butyls has significantly lower polymerization activity in saturated aliphatic hydrocarbon solvents than that in aromatic solvents.In addition,the presence of large steric hindrance structure and the electronic effect of tert-butyls also make the catalyst have better thermal stability.2.Secondly,we synthesized a variety of unconstrained geometry metallocene catalysts with tert-butyl groups by simple methods.These catalysts can efficiently catalyze the homopolymerization of ethylene and the copolymerization of ethylene with norbornene or 1-octene in saturated aliphatic hydrocarbon solvents,and the corresponding activities are closed to those in aromatic solvents.By adjusting the structure of the catalyst and the concentration of the comonomer,the properties of obtained polymer can be significantly changed,such as insertion ratio of the comonomer,molecular weight,melting point and glass transition temperature.3.Finally,we synthesized a series of organoboron cocatalysts,and evaluated their performance in saturated aliphatic hydrocarbon by using the classical constrained geometry catalysts.The cocatalyst B(C6F5)2O’Bu which containing tert-butyl structure showed high activity at the homopolymerization of ethylene and the copolymerization of ethylene with 1-octene at high temperature,and the insertion ratio and molecular weight of 1-octene of the copolymer can be improved at the same time,which showed a better performance compared with the B(C6F5)3.The species activated by B(C6F5)2OtBu have unique oxygen coordination,which increases the steric resistance and reduces the electronic density of the metal center at the same time.