Two types of two-component gels formed from pseudoenantiomeric ethynylhelicene oligomers

Langmuir. 2012 Aug 14;28(32):11939-47. doi: 10.1021/la302759k. Epub 2012 Aug 2.

Abstract

Two-component gels formed from pseudoenantiomeric ethynylhelicene oligomers in toluene exhibited two different properties depending on difference in numbers of helicenes in the two components. The combinations (M)-5/(P)-4, (M)-6/(P)-4, and (M)-7/(P)-4, which contained oligomers with comparable numbers of helicenes, formed transparent gels (Type I gels). The combinations (M)-6/(P)-3, (M)-7/(P)-3, and (M)-8/(P)-3, which contained oligomers with considerably different numbers of helicenes, formed turbid gels (Type II gels). Negative Cotton effects were observed for the Type I gels in the region between 350 and 450 nm, and were positive for the Type II gels, despite the use of (M)-oligomers for the longer components. UV/vis exhibited absorption maxima at 350 nm for the Type I gels and at 338 nm for the Type II gels. Different behaviors in gel formation processes were observed by fluorescence studies. Atomic force microscopy analysis showed fiber structures of 25-50 nm diameter for Type I gels and bundles of 100-150 nm diameter for Type II gels. The stoichiometry in gel formation also differed: The Type I gels showed 1:1 stoichiometry of the two components; the Type II gels showed no 1:1 stoichiometry, likely 1:2 stoichiometry. Using the Type I and II gels, two-layer gel systems were constructed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Gels
  • Models, Molecular
  • Molecular Conformation
  • Polycyclic Compounds / chemistry*
  • Polymers / chemistry*
  • Stereoisomerism
  • Toluene / chemistry

Substances

  • Gels
  • Polycyclic Compounds
  • Polymers
  • ethynylhelicene
  • Toluene