"Helicity Inversion": Linkage Effects of Chiral Poly(n-hexyl isocyanate)s

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 radical 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 "helicity inversion" 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).