Ethylene Polymerization Of Brush-liked Polymer Supported Catalysts

Bimodal polyethylene,owing to the combination of high molecular weight fraction and low molecular weight fraction,can improve the mechanical properties and processing performance of the material itself,and has gradually become one of the important development of high-performance polyolefin resins.At present,the most widely used methods for producing bimodal polyethylene are mainly series reactor method and single-reactor method.The single-reactor method has a low cost and simple process,and the bimodal polyethylene obtained has a very good mixing effect.It is an important process in the development of bimodal polyethylene.The single-component in-situ loading of olefin polymerization catalyst has achieved commercial scale.Our work mainly focus on polystyrene supporter with a brush topology.Four different ligands coped with central metal are designed by phenoxy-imine functionalization of the brush arm.Then ethylene polymerization by supported catalysts were carried out.Regulation and synthesis of bimodal polyethylene were on the basis of these four types of ligands.The specific work and conclusions are as follows:First is about functionalization of brush-liked polystyrene supporter.In this paper,polystyrenes with unsaturated double bonds were synthesized by atom transfer radical polymerization(ATRP),and the brush-like topology was developed and synthesized by Ring-Opening Metathesis Polymerization(ROMP).Finally,the click chemistry reaction of azide was carried out.The ultimate carrier is obtained by Aldehyde condensation.At the same time,AFM / FT-IR / NMR and other characterization methods have been demonstrated.The second part is the preparation of phenoxy-imine supported titanium,zirconium,and nickel catalysts and their polymerization properties.In order to carry out the loading and olefin polymerization of metal catalysts,it has been found that the center of titanium and zirconium metal has a better loading capacity and polymerization activity.Then with the metal center for a single point coordination,we get the final polystyrene-supported catalyst.Last part is about ethylene polymerization.We found that titanium/zirconium-derived polyethylene has good crystallization performance,and different catalysts have different activity.At the same time,GPC data found that the products obtained by one metal center with two different ligands on a brush supporter have bimodal properties,which mean the processing performance is more attractive.Therefore,the same method was utilized to modify the different active sites by adjusting different salicylaldehyde ligands on the same carrier and then coordinating with the central metal to produce bimodal polyethylene.We also explored the effect of the supporter’s morphology on polyethylene.It can be observed that the shape of the catalyst carrier play a template role in the ethylene polymerization process,and the resulting product also has a similar appearance,which can direct the research of basic theory.It means that we can affect the polymer morphology through the intervention of Carrier-template-effect,and constitute a polymer similar to the catalyst morphology.