NMR study of the comonomer effect in metallocene poly(propylene-co-1-pentene) copolymers synthesized at low temperature Articles uri icon

authors

publication date

  • March 2017

start page

  • 843

end page

  • 854

issue

  • 5

volume

  • 55

International Standard Serial Number (ISSN)

  • 0887-624X

Electronic International Standard Serial Number (EISSN)

  • 1099-0518

abstract

  • The influence of the comonomer in the synthesis ofpoly(propylene-co21-pentene) copolymers, with rac-(dimethyl-silylbis(1-indenyl))ZrCl2/Methylaluminoxane at low temperature, has been studied. Changes in the catalyst activity andmolecular weight have been analyzed as a function of copolymer composition, and associated with both content and natureof chain defects. The thorough characterization of chain-end double bonds by means of the 1H NMR technique highlights the particular chain termination pathway, which underlies the so-called comonomer effect. A specific termination mechanismis proposed based on the preferential regio-irregular interaction of the active site with 1-pentene molecules, instead of theone related to the b-H atom of the last regular inserted unit, either propene or 1-pentene.

keywords

  • comonomer effect; metallocene catalysts; microstructure; nmr; a-olefins; polyolefins; polypropylene copolymers