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Ethylene Polymerization and Ethylene-Cycoolefins Copolymerization Behaviors of Novel Mono β-Diiminato Titanium and Chromium Complexes

Author: LeiLu
Tutor: XieGuangYong
School: Central South University for Nationalities
Course: Polymer Chemistry and Physics
Keywords: non-metallocene catalysts β-diiminato ethylene polymerization
CLC: O643.36
Type: Master's thesis
Year: 2011
Downloads: 43
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Abstract


High performance cycloolefin copolymers (COC) have broad applications in many areas. The topic is to exploit highly active catalysts for controllable ethylene polymerization, which has become one of hot points in this field. In this paper fiveβ-diiminato titanium complexes with different amounts of fluorine substituents on different positions have been designed and synthesized, and their catalytic performances have been studied. It has been found that these complexes have high catalytic activity for cycloolefins and ethylene copolymerization. Further more, fiveβ-diiminato chromium complexes with different amounts of fluorine substituents on different positions have been synthesized and the catalytic performances for ethylene polymerization have been researched.This paper includes the following parts:1. The copolymerization behaviors for ethylene and norbornene or cyclopentene ofβ-diiminato titanium complexes with fluorine substituents have been researched with MMAO as cocatalyst at atmospheric pressure, and found that four complexes 4a, 4b, 4d and 4e can copolymerize ethylene and cycloolefins with high activity, in which the catalytic activity of complex 4a can reach 106g/molTi.h.atm. The fluorine substituents with different positions and amounts have great influences on the catalytic activity. The catalytic activity would be significantly increased when the ortho-positions of imine ligands were substituted by fluorine, and the more ortho-fluoro substituents, the higher activity of the complexes, but the p-fluoro substituents decrease the activity of complexes. We think the reason of ortho-fluoro substituents significantly increasing the complexes’catalytic activity , except for the fluoro substituent’s electron withdrawing effect, is mainly the formation of hydrogen bonds of o-fluorine with ethylene’s or cycloolefins’s hydrogen, which would help the ethylene or cycloolefins enrichment and coordination on the center metal, and increase the complexes catalytic activity.2. Five novelβ-diiminato chromium complexes with different amounts of fluorine substituents on different positions have been synthesized and the catalytic performances for ethylene polymerization with MMAO as cocatalyst have been researched. It was found that fluorine substituents can increase greatly the catalytic activity ofβ-diiminato chromium complexes compared with alkyl groups, in which four complexes with o-fluorine substitutients have middle catalytic activity for ethylene polymerization. The fluorine substituents with different positions and amounts have also great influences on the catalytic activity. For monofluoro substituted complexes, the complex with ortho-fluoro substituent has much higher activity than that with para-fluoro substituent. The reason of ortho-fluoro substituent significantly increasing the complexes’catalytic activity, except for the fluoro substituent’s electron withdrawing effect, is mainly the formation of hydrogen bond of o-fluorine with ethylene’s hydrogen, which would help the ethylene enrichment and coordination on the center metal, and increase the complexes catalytic activity. While the catalytic activity would decrease when more fluoro substituents were introduced.3. Five fluorinatedβ-ketoimine ligands were successfully synthesized by microwave with no solvent and catalyst. This method is very simple and has short reaction time and high yield. A new type of bridgedβ-ketoimine compounds were prepared and characterized by 1H NMR and element analysis.Above researches have important academic value and potential industrialization prospect.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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