Synthesis Of Bridged And Non-bridged Bis-(?-arylbenzyl Salicylaldimino)Ni(?)and Their Catalytic Copolymerization For Norbornene

One of the hotspots for researchers is to improve the processability of addition-formed polynorbornene materials by?-olefins or polar monomers.The highly active catalysts are the key of synthesis high performance olefin materials.Seven kinds of bis-??-salicylaldehyde-benzyliminato?nickel?II?complexes with different substituents Ni{?R₁,R₂?C₆H₂?O?CH[N?Ph-CH₂?]}₂?Ni1-Ni7:R₁=Br,CH₃,OCH₃,H;R₂=H,CH₃,OCH₃,Br?,and a strong electron-withdrawing bridged bis-??-salicylidene-fluorenyliminato?nickel?II?catalyst Ni{RC₆H₃?O?CH[N?fluorenyl?]}₂?Ni8:R=NO₂?were synthesized and characterized.The obtained crystal structure was confirmed by single crystal X-ray diffraction technique.Homo-and copolymerization of norbornene?NB?and 2-hexyloxymethylene norbornene?HN?,OC and BMA were conducted by the catalysts of B?C₆F₅?₃ or MAO.The system of Ni1,Ni3,Ni4/B?C₆F₅?₃ was used to catalyze the homo-and copolymerization of norbornene and?-olefin?1-octene?.The reaction temperature at60°C with NB/Ni ratios at 2000/1,B/Ni ratios at 10/1 were the most effective condition,the catalytic activity of norbornene is up to 10⁶g_polymerolymer mol_Ni^-1h^-1,meantime.The catalytic activity of NB and 1-octene copolymerization is up to 10⁵g _polymerolymer mol_Ni^-1h^-1.It was found from the polymerized data that when the substituent group the3-position?R₁?or the 5-position?R₂?of the salicylaldehyde aromatic ring was an electron-withdrawing group?-Br?the catalytic activity was higher than that of the electron-donating group?-CH₃,-OCH₃,H?at the corresponding position?Ni1>Ni4>Ni2=Ni3,Ni7>Ni4>Ni5=Ni6?.It is indicated that the introduction of electron-withdrawing groups in the ligands of the complex can effectively increase the activity of the catalyst.Meantime when the catalyst system was used to catalyze the copolymerization of norbornene and 1-octene,it was found that the monomer feed ratios also had a certain effect on the activity of the catalyst.As the 1-octene feed ratios increased,the activity of the catalytic system gradually decreased.The bridged Ni8 with a strong electron withdrawing group was applied to the homopolymerization of norbornene and copolymerization with polar monomer2-hexyloxymethylene norbornene?HN?combined with B?C₆F₅?₃.The Ni8/B?C₆F₅?₃system catalyzed the homopolymerization activity of norbornene to 0.35×10⁶ g_polymerolymer mol_Ni^-1h^-1,and the activity of the copolymerization of norbornene reached1.05-1.81×10⁵ g_polymer mol_Ni^-1h^-1,obtained amorphous polymer with good thermal stability?T_d>400 ^oC?,2-hexyloxymethylene norbornene has a high insertion rate.Through various tests proved that this polymerization mode is a typical addition polymerization,and the polymer has a large molecular weight of 3.78-6.04×10⁵ g/mol and a molecular weight distribution of?1.55-2.14?.The strong electron-withdrawing catalyst still has high catalytic activity in a long reaction time.When the molecular structure of the catalyst contains an electron-withdrawing group?-Br?,the catalytic activity is relatively high,indicating that the introduction of an electron-withdrawing group in the structure of the complex can effectively increase the activity of the catalyst.Meantime,it was found that the feed ratios of the monomer also had a certain influence on the activity of the catalyst.As the feed ratios of BMA increased,the activity of the catalytic system gradually decreased.After characterization by various methods,it was found that the polymerization was carried out by addition polymerization,and an amorphous polymer was obtained with good thermal stability and processability.