Investigation Of Titanium Catalysts Bearing β-Enaminoketonato For Olefin Polymerization

Olefin polymerization industry is important to our country and it contributes a lot tonational economy. To develop this industry, studying on new type of olefin polymerizationcatalysts with super efficiency is the key.On the basis of our previous work, this paperinvestigates the ethylene/cyclic olefins copolymerization behavior catalyzed by titaniumcatalysts [PhN=C（CF₃）C（H）C（Ph）O]₂TiCl₂and [PhN=C（CH₃）C（H）C（CF₃）O]₂TiCl₂whichbearing-enaminoketonato ligand. Also, we synthesize a new titanium complex[PhN=C（Ph）CHC（CF₃）O]₂TiCl₂,and investigate its ethylene polymerization andcopolymerization behavior. The detail as follows:Through the Diels-Alder reaction with dicyclopentadiene and cyclopentene, cyclohexeneand cyclooctene, we obtain three novel norbornene-derivatives,5,6-trimethylene-2-norbornene （TMN）,5,6-tetramethylene-2-norbornene （TTMN） and5,6-hexamethylene-2-norbornene （HMN）. Using [PhN=C（CF₃）C（H）C（Ph）O]₂TiCl₂and[PhN=C（CH₃）C（H）C（CF₃）O]₂TiCl₂as catalysts, the copolymerization behaviors of threecomonomers with ethylene are investigated. Note that these two catalysts can effectivelycopolymerize ethylene with comonomers and afford high molecular weight copolymers. Withthe enhancement of comonomer in feed, the catalytic activity and molecular weight of thecopolymers increased. The highest activity is4.50kg polymer/mmolTi· h and the highestcomonomer incorporation is41.9mol%. The glass transition temperature （T_g） of the polymersnot only increase with the content of comonomer but also increase with enlargment of thecycloolefin. The highest T_gin this paper is179.0C, which is HMN/ethylene copolymer with35.8mol%HMN incorporation.Because of asymmetrical β-diketone possesses two nonequivalent electrophilic centers,the condensation of β-diketone and aromatic amine would give rise to two regioisomericcompounds. Therefore, the promising performance of catalyst[PhN=C（CF₃）C（H）C（Ph）O]₂TiCl₂prompts us to synthesize its regioisomer and explores thedifferent polymerization behavior caused by such change of the ligands. New titaniumcomplex [PhN=C（Ph）CHC（CF₃）O]₂TiCl₂was fully characterized by1H and13C NMR spectraand X-ray diffraction analyses. With modified methylaluminoxane （MMAO） as a cocatalyst,the behaviors of ethylene polymerization have been explored. Under room temperature, theactivity of the catalyst is up to2.16kg PE/mmolTi· h with the weight-average molecularweight of288kg/mol, which are much higher than its regioisomer. Moreover, the copolymerization behaviors of ethylene/1-hexene, ethylene/1-octene, ethylene/norborneneand ethylene/4-methyl-1-pentene are investigated in detail. Compred with its regioisomer, forall copolymerizations, that the new catalyst exhibits higher activity, produces highermolecular weight copolymer and with higher monomer incorporation than its regioisomer.These prove that the new catalyst [PhN=C（Ph）CHC（CF₃）O]₂TiCl₂displays strongercopolymerization ability. The high1-hexene incorporation of12.5mol%can be easilyachieved at room temperature when the1-hexene concentration is0.5mol/L, which is9.41mol%higher than its regioisomer.