N. Karayannis, Sam S. Lee
Nov 1, 1983
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0
Influential Citations
3
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Journal
Macromolecular Chemistry and Physics
Abstract
Studies of various tetrahydrofuran and tetrahydropyran derivatives as modifiers of Zieglertype propylene polymerization catalysts are reported. Among methyl derivatives, ethers containing two methyl substituents on carbon atoms adjacent to the etheric oxygen provied the best activity-stereospecificity combinations (e.g. 2,5-dimethyltetrahydrofuran (1c) and 2,2,4,4-tetramethyltetrahydrofuran) (4). Significantly better stereospecificity with some loss in activity is realized when bulkier ethers such as isochroman (5) or 2-(tetrahydrofurfuryloxy)tetrahydropyran (6) are used. On the other hand, combination of one of the preceding ethers with a second modifier (bis(tributyltin) sulfide, tributyl phosphite, or triethyl thiosphosphate) results in catalyst systems characterized by very attractive activity-stereospecificity combinations. Systems of this type, containing 1c or 4, exhibit higher activity and about equal or better stereospecificity than the systems modified only with the second modifier; whereas 5 and 6 depress somewhat the activity of the latter systems but provide substantially improved stereospecificity. The steric and electronic effects introduced by the ether modifiers in the single and binary modifier systems investigated are discussed.