Propylene Polymerization with 伪-Keto-尾-Diimine Initiators Proceeds via Enantiomorphic Site Control

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• 作者：Jason D. Azoulay ; Haiyang Gao ; Zachary A. Koretz ; Gerald Kehr ; Gerhard Erker ; Fumihiko Shimizu ; Griselda B. Galland ; Guillermo C. Bazan
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：June 12, 2012
• 年：2012
• 卷：45
• 期：11
• 页码：4487-4493
• 全文大小：302K
• 年卷期：v.45,no.11(June 12, 2012)
• ISSN：1520-5835

文摘

¹³C NMR spectroscopy is used to characterize the microstructure of polypropylene (PP) obtained using a nickel 伪-keto-尾-diimine initiator activated with methylaluminoxane (MAO) at different reaction temperatures (T_rxn). The product prepared at 鈭?0 掳C has structural features that resemble an ethylene-propylene copolymer. We find that the main sequences present in this sample arise as a result of normal 1,2-insertion and that propylene sequences are predominantly isotactic (m = 88%, mmmm = 63%). There is also evidence of ethylene-like sequences as a result of 3,1-enchainment, and from 2,1-insertion. A reduction in T_rxn to 鈭?0 掳C results in a polymer that has undetectable regioirregularities and is highly isotactic (m = 93%, mmmm = 85%). Moreover, the application of stereo propagation models gives indication that the isospecificity is a result of enantiomorphic site control.