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Helix Inversion and Aggregation Behavior of Chiral Poly(N-propargylamides)

✍ Scribed by Junichi Tabei; Ryoji Nomura; Masashi Shiotsuki; Fumio Sanda; Toshio Masuda

Book ID
102484995
Publisher
John Wiley and Sons
Year
2005
Tongue
English
Weight
491 KB
Volume
206
Category
Article
ISSN
1022-1352

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✦ Synopsis

Abstract

Summary: N‐Propargyl‐2‐methyloctanamide, (1), N‐propargyl‐2‐ethyloctanamide, (2), and N‐propargyl‐2‐propyloctanamide, (3) were polymerized with (nbd)Rh^+^[η^6^‐C~6~H~5~B^−^(C~6~H~5~)~3~] as a catalyst to obtain the polymers with moderate molecular weights ($\overline M _{\rm n}$ = 15 000–57 000). The ^1^H NMR spectra demonstrated that the polymers had a stereoregular structure (cis = 100%). The polymers were proven to take a helical conformation with an excess of one‐handed screw‐sense in CHCl~3~, which was supported by their intense CD signals and large specific rotations. The signs of Cotton effects of poly(2) and poly(3) were dependent on the solvents used for CD measurement, while that of poly(1) was independent of the solvents. In CHCl~3~/THF or CHCl~3~/toluene mixtures, the sign of Cotton effect of poly(2) was inverted with changing the solvent composition at 20 °C, and the Cotton effects of poly(2) in CHCl~3~/toluene = 70/30 and CHCl~3~/THF = 80/20 were largely influenced by temperature. From the filtration and light scattering experiments of poly(2), the CD sign inversion was proved to be the screw sense inversion.

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