Synthesis and characterization of iPP‐sPP stereoblock produced by a binary metallocene system |
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Authors: | Camille Descour Tibor Macko Dario Cavallo Matthew Parkinson Gerhard Hubner Anne Spoelstra Maurizio Villani Robbert Duchateau |
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Affiliation: | 1. Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Polymer Chemistry Group, , 5600 MB, Eindhoven, The Netherlands;2. Division Plastics, Fraunhofer Institute for Structural Durability and System Reliability LBF, Materials Analytics, , 64289 Darmstadt, Germany;3. Department of Mechanical Engineering, Eindhoven University of Technology, , 5600 MB Eindhoven, The Netherlands;4. Borealis Polyolefine GmbH, , 4021 Linz, Austria;5. Department of Chemical Engineering and Chemistry, Eindhoven University of Technology Materials and Interface Chemistry, , 5600 MB, Eindhoven, The Netherlands |
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Abstract: | Stereoblock polypropylenes comprising of iPP and sPP segments are synthesized by polymerization of the following binary system of metallocenes: the Cs‐symmetric [2,7‐t‐Bu2(Flu)2Ph2C(Cp)ZrCl2] and the C2‐symmetric rac‐Me2Si(2‐Me‐4‐Ph‐Ind)2ZrCl2. Blends of samples made either by each catalyst individually (solution blend) with materials obtained with the mixed catalyst system (reactor blend) are compared. The simultaneous presence of MAO and DEZ, enhancing fast and reversible transfer of the growing chains between the two active centers, leads to the formation of a stereoblock microstructure. In this case, low molecular weight polymers are obtained. The junction between the blocks is qualitatively observed in 13C NMR. When made in toluene, the stereoblock material consists of a majority of syndiotactic sequences, whereas the ratio is more equilibrated when the polymerization was conducted in the more polar chlorobenzene. This is confirmed by the results obtained with 13C NMR, CRYSTAF, HT HPLC, DSC, SSA, WAXD, and optical microscopy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1422–1434 |
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Keywords: | block copolymers catalysis characterization isotactic metallocene microstructure polyolefins polypropylene stereoblock syndiotactic |
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