Salicylaldehyde imine ligands(1a-1c)and its titanium complexes(2a-2c)are synthesized from 3-bromosalicylic aldehyde and substituted aniline,and their structures are characterized by means of 1HNMR,13CNMR and elemental analysis.Under the action of methylaluminoxane(MAO)co-catalyst,the complexes 2a-2c are used to catalyze ethylene polymerization at atmospheric pressure.The polymers obtained are analyzed through using IR,gel permeation chromatography(GPC)and differential scanning calorimetry(DSC).The influences of ligand structure,polymerization temperature,n(Al)∶n(Ti)and catalyst dosage on polymerization behavior are investigated.Results show that under the conditions of 35℃,0.1 MPa and n(Al)∶n(Ti)=2 000∶1,the catalytic activity of complex 2a reaches the highest,being 1.40×106 gPE/(molTi·h).As the steric hindrance of the substituents on the imine benzene ring increases,the molecular weight of resulted polyethylene further increases.The weight average molecular weight(Mw)of polyethylene obtained over complex 2c reaches 8.3 × 105 g·mol-1,and the molecular weight distribution(PDI)is 2.6,indicating good controllability of the polymerization process.
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