A new semicrystalline polynorbornene was obtained by stereospecific polymerization with CrCl2(dppa)-MAO catalyst (dppa ) bis(diphenylphosphino)amine). NMR, X-ray diffraction, and modeling techniques were used, concentrating on the soluble lower molecular weight fractions, to characterize the polymer structure. The polymer presents a 2,3-exo-diheterotactic stereochemistry never observed before in the polymerization of alkenes. High symmetry, low energy chain conformations accounting for 13C NMR data are devised. Efficient crystalline packing models consistent with powder X-ray diffraction patterns and density requirements are proposed.
New stereoregularity in the stereospecific polymerization of Bulky strained olefins: crystalline diheterotactic polynorbornene
Ricci G;Boglia A;Boccia A C;Zetta L;
2008
Abstract
A new semicrystalline polynorbornene was obtained by stereospecific polymerization with CrCl2(dppa)-MAO catalyst (dppa ) bis(diphenylphosphino)amine). NMR, X-ray diffraction, and modeling techniques were used, concentrating on the soluble lower molecular weight fractions, to characterize the polymer structure. The polymer presents a 2,3-exo-diheterotactic stereochemistry never observed before in the polymerization of alkenes. High symmetry, low energy chain conformations accounting for 13C NMR data are devised. Efficient crystalline packing models consistent with powder X-ray diffraction patterns and density requirements are proposed.File | Dimensione | Formato | |
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Descrizione: New Stereoregularity in the Stereospecific Polymerization of Bulky Strained Olefins: Diheterotactic Polynorbornene
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