Citation:
TIAN Jun, WANG Baiquan, CHEN Shoushan, LIU Yu, HUANG Baotong. METALLOCENE POLYETHYLENES WITH BROAD OR BIMODAL MOLECULAR WEIGHT DISTRIBUTION*[J]. Chinese Journal of Polymer Science,
1998, 16(4): 370-376.
METALLOCENE POLYETHYLENES WITH BROAD OR BIMODAL MOLECULAR WEIGHT DISTRIBUTION*
摘要:
Seven new binuclear titanocenes with different linking bridges, unsubsti-tuted or substituted on the Cp rings, were synthesized and tested for their effect on ethylenepolymerization in the presence of MAO. The polyethylenes thus obtained had broad MWDor even bimodal GPC curves, as compared with that from two reference mononuclear ti-tanocenes. This is explained by the difference in degree of steric hindrance around the activecenter sites imposed by the bulky substituted ligands assuming different configurations in the rotation of the catalyst molecules.Lower polymerization temperatures alleviate the effect of these configuration differnces,as reflected in change in MW and Mw/Mn.This effect is not caused by decomposition or disproportionation of the binuclear titanocenes as evidenced by the stability of the catalyst.
English
METALLOCENE POLYETHYLENES WITH BROAD OR BIMODAL MOLECULAR WEIGHT DISTRIBUTION*
Abstract:
Seven new binuclear titanocenes with different linking bridges, unsubsti-tuted or substituted on the Cp rings, were synthesized and tested for their effect on ethylenepolymerization in the presence of MAO. The polyethylenes thus obtained had broad MWDor even bimodal GPC curves, as compared with that from two reference mononuclear ti-tanocenes. This is explained by the difference in degree of steric hindrance around the activecenter sites imposed by the bulky substituted ligands assuming different configurations in the rotation of the catalyst molecules.Lower polymerization temperatures alleviate the effect of these configuration differnces,as reflected in change in MW and Mw/Mn.This effect is not caused by decomposition or disproportionation of the binuclear titanocenes as evidenced by the stability of the catalyst.
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