Chiral alkylated poly(m-phenylene)s: Optical activity and thermal stability of helical structures

Risa Sone, Ichiro Takemura, Kenichi Oyaizu, Hiroyuki Nishide

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Chiral poly[4,6-bis(alkylthio)-1,3-phenylene-alt-2-methyl-1,3-phenylene] was synthesized from 1,3-dibromo-2,6-bis(3-dodecyl-2-methylthio)benzene and 2-methyl-1,3-phenylenebis(pinacol borate) as a precursor of chiral poly(thiaheterohelicene). Circular dichroism (CD) spectra that arise from the poly(1,3-phenylene) backbone inverted according to the chirality of the side chains, which indicated that a helical conformation of the polymer was induced by the interaction between the side chains. The CD intensity of the polymer increased in non-polar solvents such as hexane. The decrease in the molar CD intensity and the broadening of a fluorescence band at higher concentrations suggested that the aggregation of the polymer suppressed the formation of the helical structure. The conformational changes were monitored by the CD and the 1H NMR spectra at different temperatures. In a good solvent such as dichloromethane, the CD intensity increased, and the 1H NMR signal of benzene protons shifted to lower fields at low temperatures. In hexane, the CD spectra and the 1H NMR signals were less dependent on temperatures, as a result of the strong interaction between the chiral alkyl chains in the polymer to freeze the helical conformation.

Original languageEnglish
Pages (from-to)925-930
Number of pages6
JournalSynthetic Metals
Volume159
Issue number9-10
DOIs
Publication statusPublished - 2009 May

Fingerprint

optical activity
Dichroism
dichroism
Polymers
Thermodynamic stability
thermal stability
Nuclear magnetic resonance
Hexanes
Benzene
Conformations
polymers
Hexane
nuclear magnetic resonance
Borates
Chirality
Methylene Chloride
benzene
Temperature
Protons
Agglomeration

Keywords

  • π-Conjugated polymer
  • Chiral helical induction
  • Poly(m-phenylene)

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Chemistry
  • Metals and Alloys
  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Chiral alkylated poly(m-phenylene)s : Optical activity and thermal stability of helical structures. / Sone, Risa; Takemura, Ichiro; Oyaizu, Kenichi; Nishide, Hiroyuki.

In: Synthetic Metals, Vol. 159, No. 9-10, 05.2009, p. 925-930.

Research output: Contribution to journalArticle

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AB - Chiral poly[4,6-bis(alkylthio)-1,3-phenylene-alt-2-methyl-1,3-phenylene] was synthesized from 1,3-dibromo-2,6-bis(3-dodecyl-2-methylthio)benzene and 2-methyl-1,3-phenylenebis(pinacol borate) as a precursor of chiral poly(thiaheterohelicene). Circular dichroism (CD) spectra that arise from the poly(1,3-phenylene) backbone inverted according to the chirality of the side chains, which indicated that a helical conformation of the polymer was induced by the interaction between the side chains. The CD intensity of the polymer increased in non-polar solvents such as hexane. The decrease in the molar CD intensity and the broadening of a fluorescence band at higher concentrations suggested that the aggregation of the polymer suppressed the formation of the helical structure. The conformational changes were monitored by the CD and the 1H NMR spectra at different temperatures. In a good solvent such as dichloromethane, the CD intensity increased, and the 1H NMR signal of benzene protons shifted to lower fields at low temperatures. In hexane, the CD spectra and the 1H NMR signals were less dependent on temperatures, as a result of the strong interaction between the chiral alkyl chains in the polymer to freeze the helical conformation.

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