Linear low density polyethylene from ethylene as an o nly monomer was prepared by the combination catalyst system of Et(Ind) 2ZrCl 2 an d {2 [2 Me 4 Br C 6H 3NC(Me)] 2C 5H 3N}FeCl 2 activated with methy laluminoxane (MAO).The two catalysts were well matched in a single reactor and i t was observed that the “comonomer effect" appeared in the in situ copolymeriz ation of ethylene.The comonomer effect was some strongly influenced by the molar ratio of Al to (Fe+Zr) and the polymerization temperatures.At 60℃ and n(Al )/n(Fe+Zr)=2000,the maximum activity of the catalytic system(8 5×10\+6g/mo l·h) was 4\^25 times higher than that of homopolymerization of ethylene(2\^0×1 0\+6g/mol·h),and the value of n(Fe)/n(Zr) was 0 5.At n(Al)/n(F e+Zr)=1000,the maximum activity diminished.When polymerization temperatures incr eased,the maximum activity of the in situ copolymerization decreased and the co rresponding ratio of Fe to Zr also decayed.The copolymers made from this catalyt ic system had the characteristics of low melting point(from 132 34℃ to 70 97 ℃),low density(from 0 9467?g/cm\+3 to 0\^9283?g/cm\+3) and narrow molecular weight distribution(from 2\^29 to 1\^86).However,it’s no obvious influence of th e comonomer effect on the physical properties of the copolymers.
Branched polyethylene from ethylene as single monomer was prepared by the tandem catalyst system of {2-[2-Me C6H4 N（Me）]2C5H3N}FeCl2（1） and {2,6-[1-(2,6-Me2-4-Br-C6H4N（Me）]2C5H3N} FeCl2（2） activated with methylaluminoxane （MAO） .The products of polymerization were characterized by DSC,GPC and （）13C-NMR.The results revealed that the copolymer produced by in situ copolymerization of ethylene was a mixture of branched polyethylene and α-olefin.The content of α-olefin in the mixture was increased with increasing the molar ratio of catalysts 1/2.The MWD paramelers of polyethylene and copolymer were 28\^6 and 7\^9, respectively.（）13C-NMR spectra showed that there were ethyl groups,butyl groups and long chain alkyl groups in the copolymer.The average degree of branching of such branched polyethylene was less than 5C/1000C.
