鈥淗elicity Inversion鈥? Linkage Effects of Chiral Poly(n-hexyl isocyanate)s

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• 作者：Priyank N. Shah ; Joonkeun Min ; Chang-Geun Chae ; Naoki Nishikawa ; Daichi Suemasa ; Toyoji Kakuchi ; Toshifumi Satoh ; Jae-Suk Lee
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：November 27, 2012
• 年：2012
• 卷：45
• 期：22
• 页码：8961-8969
• 全文大小：542K
• 年卷期：v.45,no.22(November 27, 2012)
• ISSN：1520-5835

文摘

Poly(n-hexyl isocyanate)s (PHICs) with chiral moieties at both ends of their polymeric chains were synthesized by living anionic polymerizations. Such PHICs were synthesized using a bidirectional initiator (sodium naphthalenide (Na-Naph)) and terminated with a chiral acid chloride, (S)-2-acetoxypropionyl chloride ((S)-Ct). Na-Naph created a covalent linkage in the middle of the chains by radical鈥搑adical coupling. PHICs containing a chiral moiety at both ends adopted conformations with an opposite helical sense in comparison with those PHICs that had the same chiral moiety at only one end of their chain. By observing these structural differences, it was hypothesized that such a 鈥渉elicity inversion鈥?occurred in the PHICs due to the covalent linkage in the middle of the chain. Therefore, to prove this assumption about helicity inversion, a comparison study of the helical behaviors between the PHIC with the chiral moiety at both ends and the PHIC with the chiral moiety at only one end was performed. The synthesized PHICs were characterized using size exclusion chromatography-multiangle laser light scattering (SEC-MALLS), MALDI-TOF mass spectrometry, NMR spectrometry, and circular dichroism (CD).