Synthesis of New Fluorenyl Amido Dimethyl Titanium,Zirconium Complexes and Their Efficient Application on Olefin Polymerization

Author:Sun Yan Jie

Supervisor:cai zheng guo


Degree Year:2019





Polyolefins based on polyethylene and polypropylene have been widely used because of their cheap price,excellent product performance,and easy processing,which have become indispensable synthetic polymers in our daily life.The traditional heterogeneous Ziegler-Natta catalyst system(multi-active center)is still most widely used for the industry to produce polyolefin,but it gives poor control of molecular weight distribution,copolymerization performance,and living polymerization.The homogeneous catalyst,such as metallocene catalyst,can produced highly performanced and functionalized polyolefin.Among them,“constrained geometry catalysts”(CGCs)have been especially attracted attention due to their excellent copolymerization ability,high copolymerization ability,and living polymerization characteristics.The previous work focused on changing the ligand structure of CGC complexes to adjust the performance of polymerization.However,there are few systematically work focus on the effect of electronic and steric of substituent groups on the performance of polymerization.On the other hand,the homogeneous catatylst usually need highly amount of expensive cocatalyst such as MAO,MMAO,organic boron compounds for the polymerization,which make the price remain higher and restricted the further application in industrial.To design suitable complex structure for reduce the amount of cocatalysts will be directly related to the industrial application of homogeneous catalyst.Therefore,basd on previous works,we synthesized a series of(fluorenyl)(amido)dimethyltitanium complexes amd(fluorenyl)(amido)dimethylzircunium bearing different electron-donating substituents on the ligands:an adamantyl group on the amido ligand and/or a methoxy group on the fluorenyl ligand to develop high performance olefin catalyst.The titanium complexes of[(1-Adamantyl)NSiMe2(2,7-t-Bu2Flu)]TiMe2(1a);[(1-Adamantyl)NSiMe2(3,6-t-Bu2Flu)]TiMe2(1b);[(t-Bu)NSiMe2(3,6-OMe2Flu)]TiMe2(2a);[(1-Adamantyl)NSiMe2(3,6-OMe2Flu)]TiMe2(2b)and the zirconium complexes of[(1-Adamantyl)NSiMe2(2,7-t-Bu2Flu)]ZrMe2(C1);[(1-Adamantyl)NSiMe2(3,6-t-Bu2Flu)]ZrMe2(C2);[(t-Bu)NSiMe2(3,6-OMe2Flu)]ZrMe2(C3);[(2-Adamantyl)NSiMe2(2,7-t-Bu2Flu)]ZrMe2(C4)were synthesized and complexes were analyzed by 1H NMR,13C NMR spectra,elemental analysis and X ray diffraction analysis of single crystal structures.The results showed that the coordination of metal center and ligand structure followsη3-form despite the change of ligand and metal center.The Tolman Angle were calculated by the single crystal date and indicated that the steric hindrance effect of 1-amantadine and tert-butylamine to the metal center were basically similar,thus the electron effect of substituent on the structure of complex can be considered more for the future polymerization.Firstly,propylene polymerizations were conducted with titanium complexes activated by dried MMAO or(MMAO)/2,6-di-tert-butyl-4-methylphenol(BHT)in an atmospheric pressure at room temperature.The results showed that the 1-adamantyl substituent of 1a,1b-MMAO/BHT system have higher activity than dMMAO system,the activity can up to 55800 kg-polymer mol-Ti-1 h-1when the Al/Ti ratio was 200,which almost 10 times higher than dMMAO system.The reason may because the iBu2Al-(OC6H2tBu2Me)derived from the reaction of iBu3Al and BHT can be attributed to the separation of the active ion pair.The methoxy substituent complexes of 2a and 2b showed lower activity,which suggests that the introduction of excess electronic donating groups will decline the coordination capability of the mental center.The activity of polymerization can maintain to31000 kg-polymer mol-Ti-1 h-1 when the Al/Ti ratio reduced from 200 to 20,and the polymers can still available when the ratio down to 10,which provides a scientific method for the mentallence catalyst system to reduce the dependence of expensive cocatalyst in the process of industrialization.Post-polymerization of propylene and the success preparation of PE-b-iPP block polymers indicates that the complexes maintain living polymerization characteristics.The 13C NMR of polymer indicates that the PPs obtained were syndiotactic and the syn-specific propagation produced by 1b-MMAO/BHT system have rr value up to 90%.Secondly,copolymerization of ethylene with styrene,ethylene with norbornene,propylene with norbornene,ethylene with dicyclopentadiene(DCPD)used new kinds of 1-adamantyl substituent complexes 1a,1b and methoxy substituent complexes 2a,2b were conducted.(1)The results of copolymerizaion of ethylene with styrene showed that 1b had higher activity up to 192 kg-polymer mol-Ti-1h-11 with lower Tm compared to[t-BuNSiMe2(3,6-di-t-BuFlu)]TiMe2(B2),2a show lower activity and higher Tm,which means the1-adamantyl groups can improve the copolymerization ability but the methoxy groups hinder the copolymerization reaction.(2)The result of homopolymerization of norbornene and copolymerization of ethylene with norbornene indicated that 1b had high activity compared to 2a.2b had no activity on the copolymerization reaction.The13C NMR of copolymer produced by 1b was tested,and the content of norbornene was calculated can up to 42.6 mol%.(3)The results of copolymerization of propylene with norbornene showed that changing the ratio of mononmer can influence the content of norborenene of polymers,1a showed higher activity than[t-BuNSiMe2(2,7-di-t-BuFlu)]TiMe2(B1)and highest insertion rate up to 65.5 mol%.The glass transition temperature of the polymers has almost liner relationship to the content of norbornene,which means maintain living polymerization characteristic and we can get specific Tg of copolymers by the feed ratio of monomer.(4)Copolymerization of ethylene with DCPD showed that 1a and A1 have higher activity despite the concentration of monomer and reaction temperature.The insertion rate of DCPD can up to 48.4 mol%with the Tg value of 190 oC.The polymers were insoluble in trichlorobenzene solvent,which suggest another double bond of DCPD were react in the polymerization process and got crosslinked polymer.A series of new fluorine-functionalized linear low-density polyethylene(LLDPE)was achieved by the copolymerization of ethylene and fluoroalkyl-substituted norbornene(5-nonafluorobutyl-2-norbornene)using ansa-dimethylsilylene(fluorenyl)(amido)titanium complex1a and 1b as a catalyst since it has good ability of copolymerization performance.1b showed higher activity than 1a,the highest activity can up to 380 kg-polymer mol-Ti-1h-1.Polymerization can be still operated at 80℃,which suggests the complexes have good heat stability.The 13C NMR spectrum of the polymers showed that the comonomer content can be controlled in the range of 5.0mol%.The melting point(Tm)of the obtained copolymer was reduced to 83℃.The molecular weight can be reached to 2×104 order,which was higher than previously synthesized Pd catalyst system.All the results indicate that the titanium complexes can efficiently produce fluorine-functionalized linear low-density polyethylene.Finally,the zirconium complexes actived by MMAO/BHT or dMMAO as cocatalyst were conducted to the polymerization of propylene in different pressure condition.The results showed that1-adamantyl substituent C1 and C2 have higher activity with MMAO/BHT than dMMAO system,the activity can also significantly increase under high pressure.All the polymers obtained by zirconium complexes have moderate molecular weitht of 2.47.6×103 g/mol.The melting point of the polymer produced by C2-MMAO/BHT system can up to 159℃with the rrrr values to 0.97,which almost highest value in this kind of complexes.C1 and C2 were also conducted by the low amount of cocatalyst(MMAO/BHT)in the polymerization of propylene,the results showed that the activity can maintain to 1.0×105 g-polymer mol-Zr-1h-1 with Al:Zr ratio of 50.The methoxy group substituent C3 have no activity on propylene polymerization,indicated that methoxy group will make the complex completely lose coordination ability.The 2-adamantyl substituent C4 can get different short chain polymers on propylene polymerization duo to the high frequency chain transfer reaction.