13C NMR spectroscopy is the main source of information on the stereochem. of Ziegler-Natta- and related transition meta-catalyzed propene polymns. In simple cases, like those of polypropylenes formed under pure enantiomorphic-site or chain-end control, the origin of the stereoselectivity can be easily recognized from the steric pentad distribution obtained from routine 13C NMR spectra. On the other hand, the variety of innovative polymers that can now be prepd. with "high-yield" heterogeneous and metallocene-based homogeneous catalysts under hybrid, multiple, or oscillating stereocontrol represent very complex systems, which are beyond the possibilities of configurational anal. by routine 13C NMR. In such cases, high-field 13C NMR can be highly advantageous. Indeed, in this paper we show that from the Me and methylene regions of 150 MHz 13C NMR spectra of polypropylenes of various tacticities, the stereosequence distribution can be detd. at a much finer level of detail, so as to obtain an adequate exptl. basis for the investigation of the many complicated mechanisms of stereocontrol presently encountered in Ziegler-Natta catalysis.

Full assignment of the 13C NMR spectra of regioregular polypropylenes: methyl and methylene region

BUSICO, VINCENZO;CIPULLO, ROBERTA;VACATELLO, MICHELE;
1997

Abstract

13C NMR spectroscopy is the main source of information on the stereochem. of Ziegler-Natta- and related transition meta-catalyzed propene polymns. In simple cases, like those of polypropylenes formed under pure enantiomorphic-site or chain-end control, the origin of the stereoselectivity can be easily recognized from the steric pentad distribution obtained from routine 13C NMR spectra. On the other hand, the variety of innovative polymers that can now be prepd. with "high-yield" heterogeneous and metallocene-based homogeneous catalysts under hybrid, multiple, or oscillating stereocontrol represent very complex systems, which are beyond the possibilities of configurational anal. by routine 13C NMR. In such cases, high-field 13C NMR can be highly advantageous. Indeed, in this paper we show that from the Me and methylene regions of 150 MHz 13C NMR spectra of polypropylenes of various tacticities, the stereosequence distribution can be detd. at a much finer level of detail, so as to obtain an adequate exptl. basis for the investigation of the many complicated mechanisms of stereocontrol presently encountered in Ziegler-Natta catalysis.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/482416
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