Enantiomer-Selective and Helix-Sense-Selective Living Block Copolymerization of Isocyanide Enantiomers Initiated by Single-Handed Helical Poly(phenyl isocyanide)s

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• 作者：Zong-Quan Wu ; Kanji Nagai ; Motonori Banno ; Kento Okoshi ; Kiyotaka Onitsuka ; Eiji Yashima
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：May 20, 2009
• 年：2009
• 卷：131
• 期：19
• 页码：6708-6718
• 全文大小：682K
• 年卷期：v.131,no.19(May 20, 2009)
• ISSN：1520-5126

文摘

Rigid-rodlike right (P)- and left (M)-handed helical polyisocyanides (P-poly-l-1 and M-poly-l-1) prepared by the living polymerization of an enantiomerically pure phenyl isocyanide bearing an l-alanine pendant with a long n-decyl chain (l-1) with the μ-ethynediyl Pt−Pd catalyst were found to block copolymerize l-1 and d-1 in a highly enantiomer-selective manner while maintaining narrow molecular weight distributions. The M-poly-l-1 preferentially copolymerized l-1 over the antipode d-1 by a factor of 6.4−7.7, whereas the d-1 was preferentially copolymerized with P-poly-l-1 composed of the same l-1 units, but possessing the opposite helicity by a factor of 4.0. Circular dichroism and high-resolution atomic force microscopy revealed that the enantiomer-selective block copolymerizations proceed in an extremely high helix-sense-selective fashion, and the preformed helical handedness determines the overall helical sense of the polyisocyanides irrespective of the configuration of the monomer units of the initiators during the block copolymerizations. The block copolymers are rigid-rod helical polymers with a narrow molecular weight distribution and exhibit a lyotropic smectic liquid crystalline phase.