New Stereoregularity in the Stereospecific Polymerization of Bulky Strained Olefins: Diheterotactic Polynorbornene

详细信息    查看全文

• 作者：Giovanni Ricci ; Aldo Boglia ; Antonella Caterina Boccia ; Lucia Zetta ; Antonino Famulari ; Stefano Valdo Meille
• 刊名：Macromolecules
• 出版年：2008
• 出版时间：May 13, 2008
• 年：2008
• 卷：41
• 期：9
• 页码：3109 - 3113
• 全文大小：577K
• 年卷期：v.41,no.9(May 13, 2008)
• ISSN：1520-5835

文摘

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.