Liquid crystal dimers containing Cholesteryl and Triazole-containing mesogenic units

Arwa Al-shargabi, Guan Yeow Yeap*, Wan Ahmad Kamil Mahmood, Chun Chieh Han, Hong Cheu Lin, Masato M. Ito

*Corresponding author for this work

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

New liquid crystals categorised as cholesteryl dimers have been successfully synthesised through the reaction between cholesteryl 4-(prop-2-ynyloxy)benzoate moieties with n-azido(cholesteryloxy-carbonyl)alkane. All the dimers display enantiotropic mesophases. Whilst the odd-numbered dimers exhibit chiral nematic (N*), twisted grain boundary (TGB) and chiral smectic C (SmC*) phases, the even-numbered members from the same series show chiral smectic A and C. A detailed inspection on mesophase reveals that the chiral centres and the bent conformation of the odd-numbered members are essential for the induction of TGB phase. However, upon decreasing the temperature, the ratio of the transition temperatures (TSmC*-SmA*/TSmA*-I) is found to be 0.95, which indicate the second order transition according to the McMillan’s molecular theory. In addition, the X-ray diffraction study supports the presence of the smectic A phase on the even members rather than the N* by the appearance of the Bragg diffraction peaks at 190°C. A comparison study with the other analogues in which the cholesterol entity is substituted by azobenzene or biphenyl tails has been carried out to assess the relationship between the molecular structure and mesomorphic behaviour.

Original languageEnglish
Pages (from-to)219-230
Number of pages12
JournalLiquid Crystals
Volume47
Issue number2
DOIs
StatePublished - 26 Jan 2020

Keywords

  • Chiral
  • Cholesterol
  • click chemistry
  • Hybrid core
  • TGB phase
  • Triazole

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