串联催化体系制备长链支化聚乙烯

利用两种串联催化体系,Cat.I/Cat.II和Cat.I/Cat.III{Cat.I:[ArNCH-C8H3(CH2)2(C6H5)O]2 ZrBn2;Cat.II:(η5-C5Me4)Si(Me)2NtBuTiCl2;Cat.III:tans-Et(Ind)2ZrCl2)},催化了乙烯聚合,一步法制备出了长链支化聚...

Preparation of Long-Chain Branched Polyethylene Catalyzed by Tandem Catalytic System

Two tandem catalytic systems,Cat.Ⅰ/Cat.Ⅱ{Cat.Ⅰ:[ArNCH-C8H3(CH2)2(C6H5)O]2 ZrBn 2;Cat.Ⅱ:(η^5-C5Me4)Si(Me)2N^tBuTiCl2}and Cat.Ⅰ/Cat.Ⅲ(Cat.Ⅲ:tans-Et(Ind)2ZrCl2),were employed respectively to prepare long chain branched polyethylene(LCBPE)by using ethylene as the sole monomer.Ethylene is initially acted upon by Cat.Ⅰ to give ethylene oligomers with terminal vinyl groups.Subsequently,the copolymerization of the resultant oligomers with ethylene is promoted by Cat.Ⅱ and Cat.Ⅲ respectively and affords long chain branched polyethylene(LCBPE).By varying the molar ratio of Cat.Ⅰ/Cat.Ⅱ as well as Cat.Ⅰ/Cat.Ⅲ,a series of LCBPEs with controllable branching molar fraction(0.84%~3.95%)was prepared successfully.All of these obtained polymers exhibits a unimodal distribution,indicating that all of the obtained polymers are pure LCBPEs rather than the blends of ethylene oligomers and linear PE.The LCBPEs show lower crystallinity than the linear PE.Because of the entanglement of the long chain branches,the resultant LCBPEs show more obvious shear-thinning phenomenon and higher elongation.However,the lower crystallinity of the LCBPEs results in lower tensile strength.