| After Metallocene catalysts, Late transition metal have been aroused extensive attention because of its lower oxophilicity and greater functional group tolerance to early metals, it make them likely targets for the development of catalysts for the copolymerization of ethylene with polar comonomers under mild condition. Based on Grubbs type catalysts and Brookhart type catalysts, a series of Schiff base Coordinated nickel complexes have been synthesized, and its polymerization properties for ethylene were studied detailed under different cocatalysts and polymerization conditions. Studies on the copolymerization of ethylene with different type polar monomers by cited two catalysts (Cl and C5) were carried out, and the polymer products' structures have been proved characterized by IR and 'HNMR.Twelve different ligands(L1-L12) were synthesized and reacted with corresponding metal compounds to give five ortho substituted salicylaldiminato nickel(Il) complexes: {[O-(3-Cyclopentenyl) (5-CH3) C6H2-ortho-C(H)=N-2,6-C6H3 (i-Pr)2] Ni (Ph3P)(Ph)} (Cl), {[O-(3-Allyl) C6H3-ortho-C(H)=N-2,6- C6H3(i-Pr)2] Ni (Ph3P)(Ph)} (C2), {[O-(3-Allyl) (5-CH3) C6H2-ortho -C(H)=N-2, 6-C6H3 (i-Pr)2] Ni(Ph3P)(Ph)} (C3), {[O-(3-Allyl)(5-Cl) C6H2-ortho-C(H)=N-2,6-C6H3(i-Pr)2] Ni(Ph3P)(Ph)} (C4), {[O-(3-t-Bu)C6H2-ortho-C(H)=N-2,6-C6H3(i-Pr)2] Ni (Ph3P)(Ph)} (C5), and two Brookhart type catalysts: {(ArN=C(Me)-C(Me)=NAr)NiBr2) (C6), {(ArN=C(Me)-C (Me)=NAr) NiCI2} (C7) and one ortho substituted salicylaldiminato zirconium complex ({[O-(3-Cyclopentenyl) (5-CH3) C6H2 -ortho-C(H)=N-C6H5]2ZrCl2} (C8)). These compounds were characterized by MS, IR, 'HNMR and elemental analysis.Catalytic properties of six compounds (C1~C6) in ethylene polymerization were studied detailed. With Ni(COD)2 and Al(7-Bu)3 as the cocatalyst, the effects of different polymerization conditions on catalytic properties were discussed. High activity or distinctive catalytic properties of these catalysts systems were found.In the polymerization of (Cl ~C5)/Ni(COD)2, the catalytic activities and the polymer's molecular weight both decreased with the increase of catalysts' concentration. While elevating reaction pressure, The catalytic activities and the polymer's molecular weight all increased. With prolongation of polymerization time, the catalytic activities gradually declined while the molecular weight of PE increased. Effect of temperature on the catalytic properties of these catalysts systems was very distinct. Under normal temperature, the polymerization activities were very low. While increasing the reaction temperature to 45℃, the catalytic activities and the molecular weight reached climax. Above 60℃, the catalysts deactivated badly, therefore both the catalytic activities and the molecular weight declined rapidly. Under the optimal polymerization conditions, the activities of these compounds can reach: 4.34 X 105 g PE/(mol Ni hr), 2.86 X 105 g PE/(mol Ni hr), 2.65 X 105 gPE/(moi Ni hr), 6.31 X 105 g PE/(mol Ni hr) and 4.05 X 105 g PE/(mol Ni hr) respectively, and the products' molecular weight can reach: 4.13 X 104, 1.73 X 104, 2.13 X 104, 2.27 X 104 and 2.07 X 104 respectively.With AI(i-Bu)3 as the cocatalyst, these catalysts (Cl-C5) also can catalyze ethylene polymerization effectively while controlling the molar ratio of Al(i-Bu)3to catalysts slightly higher than stoichiometric ratio. In polymerization systems of Cl/Al(i-Bu)3, C2/Al(i-Bu)3 and C4/Al(i-Bu)3, There all existed a length of induction time. The excellent molar ratio of Al(i-Bu)3to these catalysts were respectively 10, 5, 5 and the excellent polymerization temperatures were about 60℃. The polymerization performance close matched with the catalytic system while Ni(COD)2 as cocatalyst. For C5/ Al(i-Bu)3, the induction time was not observed and the excellent molar ratio of Al(i-Bu)3to catalysts was 20. Compared with C5/ Ni(COD)2, the excellent polymerization temperature was identical and the catalytic activity was twofold approximately while the products' molecular weight was almost consiste... |
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