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Microtacticity of polypropylene fractions produced by different active sites of heterogeneous Ziegler–Natta catalyst
Author(s) -
Xu Junting,
Yang Yiqing,
Feng Linxian,
Kong Xiangming,
Yang Shilin
Publication year - 1996
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19961031)62:5<727::aid-app2>3.0.co;2-y
Subject(s) - tacticity , fractionation , polypropylene , catalysis , polymerization , polymer chemistry , stereospecificity , natta , ziegler–natta catalyst , chemistry , carbon 13 nmr , materials science , chemical engineering , organic chemistry , polymer , engineering
Polypropylene (PP) prepared with the MgCl 2 /TiCl 4 –AlEt 3 /Ph 2 Si(OMe) 2 catalyst system was fractionated by a preparative temperature rising elution fractionation (TREF) technique in the wide temperature range of room temperature to 130°C. The results of fractionation showed that there were plural active sites in this heterogeneous catalyst. Some key fractions were selected for characterization of 1 H‐ and 13 C‐NMR. 1 H‐NMR results suggested that the fractionation takes place according to tacticity. Based on analysis of 13 C‐NMR, it was concluded that the polymerization mechanism proceeding on highly stereospecific active sites was active site‐controlled and nonstereospecific active sites were able to convert into syndiotactic active sites during the polymerization, which led to the formation of a syn‐diotactic block. © 1996 John Wiley & Sons, Inc.