Synthesis Of Late Transition Metal Catalysts And Application In Olefin Polymerization

Late transition metal catalysts had many advantages,they had high catalytic activity for olefin polymerization and the polymer produced had narrow and unimodal molecular weight distrubutions.The steric effect and electronic effect of different substituent of late transition metal catalysts had great influence on polymerization activity.This work had important significance for the investigation olefin polymerization.In this thesis,a series of?-diimine ligands containing diphenylmethyl structure were synthesized.These catalysts had high polymerization activity and thermal stability.The polymerization of norbornene and ethylene was carried out under synthesized nickel catalysts activated by MAO or DEAC.The effect of different substituents?-CH3,-F,-OCH3?on the position 4 of phenyl ring and hydroxyl group on the thermal stability of catalyst and reaction activity was investigated.The polymerization conditions,such as temperature,n?Al?/n?Ni?,pressure,reaction time and cocatlyst had influence on the polymerization activity and polymer structure.Structure of polymer was characterized by FT-IR,NMR,DSC and TGA.The main results were as follows:1.Used nickel?II?dibromide dimethoxyethane adduct?NiBr₂?DME??and nine ligands containing diphenylmethyl structure,nine different structure?-diimine catalysts A-CH₃,A-F,A-OCH₃,B-CH₃,B-F,B-OCH₃,C₁,C₂,C₃ were successful synthesized and characterized by ¹H-NMR and FT-IR.2.The catalysts containing methyl or fluoro group had low activity towards ethylene homopolymerization activated by DEAC,only 10⁴gPE/molNi·h.The catalyst with methoxyl group had high activity towards ethylene homopolymerization activated by DEAC,reached 10⁶gPE/molNi·h.The catalyst with methyl and hydroxyl group had high activity and thermal stability towards ethylene homopolymerization,reached 4.50×10⁶gPE/molNi·h at 70?.The change of polymerization conditions had influence on the degree of branching.and melting point.Branched polyethylene was obtained and characterizate by ¹³C-NMR and DSC,the degree of branched polyethylene was 40-80/1000C and melting point was 60-80?.Two kinds of asymmetric structure catalysts have different catalytic activity.3.The catalyst containing fluoro group had high activity and thermal stability towardsnorboenenehomopolymerization,reached6.3×10⁵gPE/molNi·h.addition-type polynorbornene was obtained,characterizate by¹H-NMR,FT-IR and TGA.The thermal decomposition temperature of polynorbornene was 450?.