Mechanism of the transformation of a stiff polymer lyotropic nematic liquid crystal to the cholesteric state by dopant-mediated chiral information transfer

Mark M. Green, Stefania Zanella, Hong Gu, Takahiro Sato, Giovanni Gottarelli, Salil K. Jha, Gian Piero Spada, Anne Marie Schoevaars, Ben Feringa, Akio Teramoto

Research output: Contribution to journalArticle

Abstract

In this work the lyotropic liquid crystal nematic state of poly(n-hexyl isocyanate) (PHIC) was converted to the cholesteric state by doping with a variety of chiral small molecules and with optically active polyisocyanates. Circular dichroism experiments in dilute isotropic PHIC solutions show that several of the small molecules used as dopants in the liquid crystal work cause an excess of one helical sense in the otherwise helically dynamically racemic PHIC. Both the helical sense and excess of this sense in dilute solution correlate to the cholesteric sense and twisting power of the same dopants in the concentrated PHIC liquid crystal solutions. The experimental results are consistent with a mechanism of cholesteric formation in which the chiral dopants displace slightly the otherwise equal population of the dynamically interconvertable mirror helical senses of the PHIC, which is then further amplified by the liquid crystal matrix. Direct evidence for the amplification of the intrinsic helical sense excess of the polyisocyanate by the liquid crystal state could be demonstrated by comparing the cholesteric properties of systems doped with polyisocyanates in which the ratio of the mirror helical senses of the dopants in two compared experiments are identical but in one experiment the helical senses could interconvert and in a separate experiment could not interconvert. The amplification mechanism is driven by the reduction in population of the mobile kinked helical reversals which likely act as 'bad neighbors' to the local liquid crystal organization.

Original languageEnglish (US)
Pages (from-to)9810-9817
Number of pages8
JournalJournal of the American Chemical Society
Volume120
Issue number38
DOIs
StatePublished - Sep 30 1998

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Liquid Crystals
Nematic liquid crystals
Liquid crystals
Polymers
Doping (additives)
Polyurethanes
Amplification
Mirrors
Experiments
Molecules
Dichroism
Circular Dichroism
Population
poly(n-hexyl isocyanate)

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  • Chemistry(all)

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Mechanism of the transformation of a stiff polymer lyotropic nematic liquid crystal to the cholesteric state by dopant-mediated chiral information transfer. / Green, Mark M.; Zanella, Stefania; Gu, Hong; Sato, Takahiro; Gottarelli, Giovanni; Jha, Salil K.; Spada, Gian Piero; Schoevaars, Anne Marie; Feringa, Ben; Teramoto, Akio.

In: Journal of the American Chemical Society, Vol. 120, No. 38, 30.09.1998, p. 9810-9817.

Research output: Contribution to journalArticle

Green, MM, Zanella, S, Gu, H, Sato, T, Gottarelli, G, Jha, SK, Spada, GP, Schoevaars, AM, Feringa, B & Teramoto, A 1998, 'Mechanism of the transformation of a stiff polymer lyotropic nematic liquid crystal to the cholesteric state by dopant-mediated chiral information transfer', Journal of the American Chemical Society, vol. 120, no. 38, pp. 9810-9817. https://doi.org/10.1021/ja981393t
Green, Mark M. ; Zanella, Stefania ; Gu, Hong ; Sato, Takahiro ; Gottarelli, Giovanni ; Jha, Salil K. ; Spada, Gian Piero ; Schoevaars, Anne Marie ; Feringa, Ben ; Teramoto, Akio. / Mechanism of the transformation of a stiff polymer lyotropic nematic liquid crystal to the cholesteric state by dopant-mediated chiral information transfer. In: Journal of the American Chemical Society. 1998 ; Vol. 120, No. 38. pp. 9810-9817.
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