Synthesis of Allyl-Terminated Syndiotactic Polypropylene: Macromonomers for the Synthesis of Branched Polyolefins
Low molecular weight syndiotactic polypropylene (syndio-PP) with an olefin end group was synthesized using methylaluminoxane-activated bis(phenoxyimine)titanium dichloride ((PHI)2TiCl2) catalysts. Propylene enchainment occurs by a 2,1-insertion mechanism, and termination by β-hydride elimination pro...
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Published in | Macromolecules Vol. 38; no. 15; pp. 6259 - 6268 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Washington, DC
American Chemical Society
26.07.2005
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Subjects | |
Online Access | Get full text |
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Summary: | Low molecular weight syndiotactic polypropylene (syndio-PP) with an olefin end group was synthesized using methylaluminoxane-activated bis(phenoxyimine)titanium dichloride ((PHI)2TiCl2) catalysts. Propylene enchainment occurs by a 2,1-insertion mechanism, and termination by β-hydride elimination produces low molecular weight syndio-PP with allyl end groups. Several new (PHI)2TiCl2 complexes with various ligand modifications were found to display a wide range of activities (turnover frequency (TOF) = 3−1200 h-1) and syndiospecificities ([rrrr] = 0.46−0.93) for propylene polymerization. While the TOF increases with increasing reaction temperature and propylene concentration, the molecular weight of the resulting macromonomer shows little variation. This provides strong support for a chain-transfer mechanism involving one molecule of propylene. The allyl-terminated PPs reported herein can be used to synthesize branched polyolefins or other new polyolefin architectures. |
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ISSN: | 0024-9297 1520-5835 |
DOI: | 10.1021/ma050735u |