Stereoblock Polypropylenes Prepared by Efficient Chain Shuttling Polymerization of Propylene with Binary Zirconium Catal
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ARTICLE
POLYMER SCIENCE
https://doi.org/10.1007/s10118-020-2446-2 Chinese J. Polym. Sci.
Stereoblock Polypropylenes Prepared by Efficient Chain Shuttling Polymerization of Propylene with Binary Zirconium Catalysts and iBu3Al Xiao Yina, Huan Gaoa, Fei Yanga, Li Pana*, Bin Wanga, Zhe Maa, and Yue-Sheng Lia,b a Tianjin Key Lab of Composite & Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China b Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
Electronic Supplementary Information Abstract Stereoblock polypropylenes bearing isotactic, atactic, and syndiotactic polypropylene segments were successfully prepared by dry methyl aluminoxane activated binary catalysts system, Ph2CFluCpZrCl2 and {Me2Si(2,5-Me2-3-(2-MePh)-cyclopento[2,3-b]thiophen-6-yl)2}ZrCl2, in the presence of iBu3Al as a chain shuttling agent. By studying the catalyst activity, chain transfer efficiency, and reversibility of chain transfer reaction of each catalyst system, as well as the molecular weight and polydispersity of the resulting polymers, the alkyl exchange reactions between the zirconium catalyst and different main-group metal alky were estimated, respectively. Based on the optimized react condition, the chain shuttling polymerization was conducted by binary catalyst system in the presence of iBu3Al under both atmospheric and high pressure. Resultant polymers were identified as stereoblock polypropylenes according to microstructure and physical properties analyses by 13C{1H}-NMR, DSC, and GPC. Keywords Stereoblock polypropylenes; Chain shuttling polymerization; Zirconium catalyst; Chain transfer reaction Citation: Yin, X.; Gao, H.; Yang, F.; Pan, L.; Wang, B.; Ma, Z.; Li, Y. S. Stereoblock polypropylenes prepared by efficient chain shuttling polymerization of propylene with binary zirconium catalysts and iBu3Al. Chinese J. Polym. Sci. https://doi.org/10.1007/s10118-020-2446-2
INTRODUCTION Polypropylene (PP), as one of the important families of polyolefin resins, can be molded or extruded into many plastic products in which toughness, flexibility, light weight, and heat resistance are required. Essentially, the pendant methyl group (CH3) can adopt a number of tacticities, or spatial arrangements in relation to the carbon main-chain, but in practice only the isotactic form is marketed in significant quantities.[1] Since its discovery in 1954 by Giulio Natta and co-workers,[2] as a crystalline thermoplastic with a melting point of approximately 170 °C, isotactic polypropylene (iPP) keeps on sparking the curiosity of chemists on account of its strong tensile strength and low cost. However, the poor impact strength and brittleness greatly limit the application of iPP. Therefore, modification of iPP with improved physical performance has attracted wide attention.[3] Considering that the stereochemistry of polyolefins strongly influences their properties, PP consisting of blocks of low-isotactic (soft block) and high-isotactic/s
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