Induced circular dichroism as a probe of handedness in chiral nematic polymer solutions

Jian Xin Guo, D. G. Gray

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Achiral dyes in isotropic (acetyl)(ethyl)cellulose (AEC) solutions display no induced CD signals irrespective of acetyl content, polymer concentration or dye content. When dissolved in anisotropic AEC solutions, the dye molecules show strong induced CD bands that disappear when the phases are heated above the anisotropic/isotropic phase transition temperature. The liquid crystal induced circular dichroism (LCICD) spectra for the dyes in a series of well-characterized AEC mesophases, whose handedness depends on solvent and acetyl content, reveal that the sign of the LCICD signal is determined by the supramolecular structural features of the host matrices. Thus, acridine orange (AO) dissolved in a left-handed liquid crystalline AEC solution displays a negative LCICD whereas a positive LCICD was observed when the AO is dissolved in a right-handed AEC mesophase. The sign and intensity of the LCICD signals change with acetyl degree of substitution, solvent and temperature. In all cases, changes in sign of the CD peak correlated with changes in handedness of the chiral nematic structure, and the intensity of the CD peak increased with increasing chiral nematic pitch for a given solvent and polymer concentration. Induced circular dichroism is thus a useful probe of chiral nematic structure in these systems.

Original languageEnglish (US)
Pages (from-to)571-580
Number of pages10
JournalLiquid Crystals
Volume18
Issue number4
DOIs
StatePublished - 1995
Externally publishedYes

Fingerprint

Liquid Crystals
handedness
Dichroism
Polymer solutions
dichroism
Liquid crystals
Coloring Agents
liquid crystals
probes
polymers
Dyes
dyes
Acridine Orange
Polymers
cellulose
Substitution reactions
Superconducting transition temperature
Phase transitions
Cellulose
Crystalline materials

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Induced circular dichroism as a probe of handedness in chiral nematic polymer solutions. / Guo, Jian Xin; Gray, D. G.

In: Liquid Crystals, Vol. 18, No. 4, 1995, p. 571-580.

Research output: Contribution to journalArticle

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AB - Achiral dyes in isotropic (acetyl)(ethyl)cellulose (AEC) solutions display no induced CD signals irrespective of acetyl content, polymer concentration or dye content. When dissolved in anisotropic AEC solutions, the dye molecules show strong induced CD bands that disappear when the phases are heated above the anisotropic/isotropic phase transition temperature. The liquid crystal induced circular dichroism (LCICD) spectra for the dyes in a series of well-characterized AEC mesophases, whose handedness depends on solvent and acetyl content, reveal that the sign of the LCICD signal is determined by the supramolecular structural features of the host matrices. Thus, acridine orange (AO) dissolved in a left-handed liquid crystalline AEC solution displays a negative LCICD whereas a positive LCICD was observed when the AO is dissolved in a right-handed AEC mesophase. The sign and intensity of the LCICD signals change with acetyl degree of substitution, solvent and temperature. In all cases, changes in sign of the CD peak correlated with changes in handedness of the chiral nematic structure, and the intensity of the CD peak increased with increasing chiral nematic pitch for a given solvent and polymer concentration. Induced circular dichroism is thus a useful probe of chiral nematic structure in these systems.

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